I got some on Amazon that work fine, admittedly my car's a 2003 model so it may not be as fussy as newer models but I just had a quick look and these seem to fit the bill
GBrite - 2x Bax9s 8 smd led reverse bulbs for Audi A3 S3 RS3 8v Xenon White Canbus Error Free : Amazon.co.uk: Automotive
Only a tenner so worth a punt I reckon. I hate dim reversing lights too.
Problem solved, to cut a long story short I bought a similar Audi motor/linkage assembly, swapped the motors over, and did some judicious grinding on one of the linkages to achieve the desired throw on the wiper arms. More of a faff than it should've been but I got there in the end. If anyone has the same problem finding this particular linkage (8P2955023G) feel free to drop me a line and I'll be happy to explain in more detail, and thanks for everyone who offered help.
