Is there a list of white metal kits that have been produce over the years,such as Gem Loco kits etc.

NGS Handbook used to have a list of who made what loco kit.
Another good reason for joining.

Try searching the kit built locos thread on the Forum.

There has been a thread about Foxhunter (I think) and Hughes there, at least. Even if lists are not complete, they will give a good idea, of what's been around

Martyn