Right well after a good few months of settling into Caddy life - I am happy to report that it's been a hoot.
The BXE engine and 5-speed gearbox are ok but the van isn't setting any speed records, nor is it fantastically economical.
I'm getting around 41.5mpg long term which in my mind aint fantastic.
I was in two minds about remapping the ECU and swapping out the 5-speed for a 6-speed but this seems like it might over-burden an already challenged engine (BXE known for throwing rods.......perhaps 2% of BLS/BXE fail this way).
So I decided to go down the BKD 2.0TDi PD140 route.......and DSG......
I've bought a donor car today with 50k on the clock and am going to set about looking at wiring diagrams in readiness for when it arrives.
The BXE engine is going into my 58 reg Passat 1.9Tdi BXE which is sitting in the yard with a rod through the block !
Looks like I will have a low mile 5-speed gearbox going spare (68k) and driveshafts to suit.
Will likely have a BXE turbo, injectors, top end, de-immo'd ECU too.

Turbo Power........