Hi Dan,
I too am from the area (well Taunton) have been doing something similar for years. I have done it up in Cumbria as well.
Try lambbank.co.uk we ended up with 5 lambs for a grand total of £25! They came from two seperate sources, 3 were free as they are wonky so to speak and the other two were £25 for the pair. Becomes really worth it.
If you need any advice feel free to drop me a pm.