Spoke to the chap at ZF who was helpful, although the conversation was very disappointing. I suppose from his point of view he has to go with the official line.
Although he is still not sure if it is possible to bolt a new valve control block to the old DMY.
He confirmed that TCU and Valve block are coded at ZF prior to being sent to Audi for more software (driving style etc.)
Although TPS gave me a price for the valve control block on its own, he is sure it is not available separately.
He also was worried that even if I could find a used or new valve block it would need to be coded to my TCU, which is mated to my ECU.
So, I have reached out to a few contacts and found a local software genius who thinks he will be able to recode the refurbished DMY to my FBG TCU. He has done several X5's and was the only chap who could recode a TT dash the other day for a friend in the trade.
My guys are putting it back together and I will have it trailed over there.
Thanks for your help and I will of course let you know if this guy manages to do the impossible!