You will have to ask Nik what his lead time is.
As far as quality.....Ceriatone is going to be better made than almost anything that has a Marshall logo on it. I refer, of course, to what is being made today, not the hand wired amps of 30 years ago.
Nik builds as good a amplifier as anybody on the planet. But keep in mind, stuff (especially tubes) can be damaged during shipping. No builder would ever ship a dead amp, but it is not unheard of for a tube to fail during the shipping process.  Otherwise, that amp will only need maintenance for the next 3-4 decades.
Good Luck

Not sure what you mean by, "Why the preference for 4 ohms?"
What amp are you referring to?
The Fender's came with an OT that had a 4 Ohm tap only.  So there was no "preference", because there was no choice.
The Ceriatone Vibro Champ has an impedance selector, so you have a lot of flexibility with that amp.

Our Ceriatone Vibro Champ is a head, so we run it with all kinds of different cab/speaker options.  Our silver face Fender has one of those modern day Jensen's, I believe it s a CR-8, gold label with red lettering, 4 ohms of course.  That is a surprisingly good speaker, has more bass response than you might expect. That is about all the help I can give you.
Good Luck                                                         

You will need to change rectifiers, and probably some components in the cat bias circuit. That would be the easy part.  If you email Nik at Ceriatone he will get back to you real fast. He can advise you about the necessity of changing your Output Transformer, and any other details.
Good Luck

You could  fill a book with information regarding the topics that "grod915" has discussed. I have heard a lot of "Half Power" switches over the years, and a lot of guys have praised them.  I just have never felt they worked that well. And do not confuse half power with half volume.  Again, "grod915" has mentioned a VVR. I think those are a better solution for most circumstances. Of course, the best solution is trying as many different options as you can, so your ears can have a vote.
Good Luck

Wow !
That really is a handsome little amp.  We have a Vibro Champ clone that I built from one of Nik's kits.  Looks like the "Ultra" switches out the tone stack.  Maybe that is kind of like a "Tweed" switch.  At any rate.... I do not think most people realize what a great sounding amp this is.  I guess they are put off by its size or low wattage, or maybe the 8" speaker that came in the old Fenders.  Ours is a head, it is as good a guitar amp as any others we have, and we have a lot of amps.  For recording, small gigs, gigs with good PA/Monitor support these amps are awesome.  They have a great overdriven sound and a great clean tone as well. And that Tremolo.....
That is a great speaker you chose.  You put something together that may well be with you for the rest of your life.
Good Luck

Did you add the MV? Just a guess, but it sounds like either a lead dress problem, or maybe you need to play with the Presence. Does the Presence affect it at all?  Maybe adjust the neg feedback to that circuit via the 100k or the cap on the P Pot.  I really don't know, but those are a couple things to try.  You may need to get some help from The Garage.
Good Luck

The instrument cable is a bad idea, but does it (the cable) still work?  Could be a coincidence, but smoke and smell are a bad sign. Something died in your amp, smoke and smell is usually associated with caps and transformers. Start with a visual inspection. To measure DC resistance of your OT you will have to disconnect the wires, unless the OT is obviously a lost cause.
Good Luck

 Do you have any idea why the fuse gave up?
If there are no obvious problems, I would pull the power tubes,  fire up the amp, and turn off  the stand by (put it in play mode) . If you want to read voltages, (plate, bias, screen, etc.) go ahead. If the fuse does not blow, turn off the amp, put the tubes back in, turn the amp back on and see what happens.

Can you take some voltage readings with all the pots on Zero, the Trem turned off, and the power tubes out of the chassis? It could be a lot of things, including bad power tubes. You can put the power tubes back in and see if your volt readings change.
Do you have a light bulb limiter?

Can you get Eminence in the UK ?
I have used The Tonker in several Twin Reverbs. They are a heavy magnet speaker, and can take quite a bit of power. The Lynch V12 might also be a good choice if you are concerned about blowing up a single 12" speaker.
Good Luck

http://www.eminence.com/guitar_speaker_detail.asp?model=THETONKER&speaker_size=12&SUB_CAT_ID=4


http://www.eminence.com/guitar_speaker_detail.asp?model=LYNCHSUPERV12&speaker_size=12&SUB_CAT_ID=4

You say your speaker is 6,8     
Do you mean 6.8 ?
If so, that means you have a 8 ohm speaker.  You should use the 8 ohm selector for your amplifier.

The "correct" orientation is toward the ground/low impedance side of the circuit.  In your case you would want to have the black band facing the pots/front panel, not the preamp tubes/back panel.
With that said, I have never been able to hear a difference.  If there are any concerns for recording, long term stability, aid to electron flow, etc. etc. I could not speak to that.  I have always installed them in the "correct" manner, though I am not completely convinced of the importance.
Hope That helps

Hey Kevin -
Wyatt has demonstrated very clearly what I mentioned to you in a PM.  If you rob one of those inputs to make a clean channel you will loose the gain of the other.   That is why you would need another tube to accommodate a clean channel. Then there are the issues of the shared tone stack and other problems. 
Again, as wyatt says, you would be better off worth a different amp, instead of chopping up the one you just worked so hard on to build.  Try  playing with pedals, pre-amp tubes, and guitar volume roll-off and see if you can reach a happy medium.  Your amp is still very new to you, the two of you have some getting acquainted with to come.   My experience is that it is easier to dirty a clean amp than it is to clean up a dirty one.  But I think it is within reach of finding a compromise with your 100 watt 800.
Good Luck

Canada has a very good tube dealer (maybe more than I know)  http://thetubestore.com/

We use mostly SED and TAD.  The fact is you will just have to try a few to see what you hear.  I do not think you need to spend the large amount of money that is NOS tubes, unless your income is not a factor.
For guitar amps there are basically only three tube manufactures:
1.  JJ
2.  New Sensor
3.  Shuguang
Virtually every (modern day) tube you buy will be made by one of these three companies, including the tubes I recommended. Do not pay extra for Gold anything (pins etc.)  do not pay extra for balanced preamp tubes of any kind.  Do not hesitate to pay a few extra dollars to a good dealer for the same tube you might be able to buy from an unproven source.  A good dealer will burn in, and subsequently, cull a large number of the tubes they purchase.  The cull rate might be as high as 20%. It is worth a few extra dollars to know the tubes you buy have gone through at least this cursory 24-48 burn test.  Do not pay more for "quiet tubes".  There is no way to guarantee micro phonics, or rather the lack of it. 
Matched power tubes are not "necessary" but it is a big convenience, and has always been worth the extra money to us to have matched power tubes. That's about it.
Good Luck