I part exchanged my old car at the beginning of Nov & forget to take the old tax disc to send to Swansea for a refund (6 months, £90, worth having!). By the time I got home & rang the dealer (60 miles away) they had already removed it, filled in the form for me, & posted it 
DVLA say allow 6 weeks before chasing, so maybe it does take that long, but I'm not 100% sure that the dealer was sufficiently literate to copy out my name & address exactly as it appeared on the reg document & the claim form says if you don't you don't get the refund & you don't get the tax disc back either.
Anybody know?