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.
