Colin, this is cracking stuff! A town house is on my list of things to build but was dreading it so hats off to you! Looking forward to seeing this one finished.
For inspiration you've got Google images but you can also take a wander around the local town and it wont be long until you see something that catches your eye.
As the other chaps have said books are a great source. Nip down to your local libaray and in the reference section they should have books like those 'Then and Now' publications or 'Such and Such Town as it was', you know the sort I mean.
I'm a bit lucky as I have access to the university library and there are shelves of books with images of Victorian Britain, I've literally spent days trawling through them!

There's even books for the architectural boffs with floor plans etc of Victorian housing. If you get desparate get yourself down to Chez Thunderchicken for a weekend and I'll take you there so you can have a trawl yourself..... via the pub of course.
