hi there you could try easy
http://www.easy-arch-salv.co.uk/ they are not cheap but you could find what you are looking for. or Glasgow architectural salvage
http://www.glasgowarchitecturalsalvage.co.uk/public/live/door_search.php there used to be loads of antique places along the river beside the Glenlee but they burnt down...

there is a place near Stirling that also does salvage stuff... another place worth considering is Great Western Auctions
http://www.greatwesternauctions.com/ or the auction place on the south side (beside Queens Park train station - can't remember the name of it) - they sometimes have doors... if I think of any more, I will let you know...also keep your eye on skips...seriously, Mr P got a door (albeit not one with glass in) for his tenement in Glasgow from a skip and I've salvaged decorative woodwork which was being ripped out to make way for a trendy minimalistic makeover job...as it was the same street, it matched perfectly (used to fix a damaged door surround)... good luck