Car appreciation... the aesthetics, the engineering, etc

Front it out. Probably.

You buy something older, you will spend the whole time comparing it to the fantasy of what might have been, if only you had waited 3-4 months.

Also, how quickly will an "older/ cheaper" arrive?
and how much use would there be in the time difference?

EDIT: I have totally misread your post, I read it as they will get the van in Nov, and get it for you in Jan.

I'd mentally prepare for it not to be delivered by VW until March/April. There's a lot of chat over on Pistonheads (the lease thread specifically) about delivery of VAG group cars being pushed back time and time again, so your situation doesn't surprise. I'd stick with it though, just temper your expectations on when you'll get it.

How long will CJL take to turn it around once they get their hands on it?

My two cents is...You know what you want. You have found a company (admittedly with terrible communications thus far) that will do it and do it to a good standard. You might regret not getting what you want over what is likely to be a matter of a few weeks.