I had a very similar situation to you with my A4 2.5TDi Q in October at 128k miles, after the timing belt skipped. What happened to yours? I decided to get mine done, whats it worth as a non-runner? Few hundred for parts maybe.....
I paid £1500 plus vat for another engine and paid my local garage whom I trust £1000 to swap them over which will give you an idea of cost. However I was unlucky in that within 6 days the second engine also skipped its timing belt
Another engine was fitted under warranty by the engine supplier but it took almost a month and a lot of damage to the car before I had it back. (I am still in discussion ref damage reimbursement.)
What I hadn't banked on was just spending another £1200 with a local specialist getting the timing set properly for the engine and fuel pump, and replacing other odd and sods such as MAF, fan viscous coupling etc. So far I have spent in the region of £4k and it still doesnt go like the old one did.
I thought I was safe in using a garage I trusted, but due to the engine failing through no fault of my own I ended up in a situation where an unknown garage did the warranty work.
I hope you have a better experience than I did! Good Luck!