UK Dealer Problem with Part of Rear diff on 20v Coupe Quattro

["Karl Harrison" <karl@harrison.prestel.co.uk>]

Recently I bought a used 20v Coupe Quattro for a good price as the diff
seals were leaking, I thought this a standard seal replacement job for a
local garage which is very familar with Audi's.I did get the dealer to quote
but it was too costly. Anyhow I ordered the parts from the main dealer and
they arrived 2 days later, I had the garage do the job, except they could
not complete it as the nearside seal was the wrong one! The dealer was 100%
certain the part was correct, however the local garage went over and checked
the fiche with the parts manager and they then agreed the part is NOT listed
on the fiche and that they would need to fax Audi in Germany to get the
details, What kind of service is this?
My local garage would not remove the seal from the nearside in the event the
dealer could not replace it and has taken the measurements of it which is
the info faxed to Audi. over 6days  later no response from the dealer!
Why is the fiche info incorrect?
Engine is type 7A.

Has anyone sucessfully replaced both rear diff seals on a 1991 Coupe Quattro
20v? What part numbers did you use?