Is there a variety of self-fertile peach I could grow in an unheated greenhouse in a container?
Have a look here http://www.readsnursery.co.uk/categories/Peach-Trees/ - I'm sure you'll find one to suit you. They're a really good nursery and very helpful if you email them.
I have no connection with them other than as a very satisfied customer.
Yes, it's a great variety. I grow it outside in my south-facing front garden in the east midlands and it never fails to set fruit.