What is covered under band 3

[di]

I had two teeth extracted and was given a temp denture until my gums healed. I can't have plastic for health reasons so was told I could have a chrome denture. They are now refusing to give me the permanent denture unless I pay again, another £198. They claim the temp denture is all I'm entitled to in one course of treatment. It's taken well over 2 months because the dentist only works part time so from seeing him in November last year I didn't get the temp denture and extractions until Jan 29th 2010 and I can't see him again till May. He said he would call me back in 3 months when my gums had healed to do a permanent denture but then I got a threatening letter demanding payment for the supposedly completed course of treatment.
I wasn't given a copy of any treatment plan although they claim I signed one that said I'd only get  only the plastic temp denture. I couldn't read it as I didn't have my glasses but the dentist said I'd get the temp one changed once my gums had healed. NO mention of time limits or exclusions. I had a recommended treatment plan from a specialist at a dental hospital which was fully discussed and agreed verbally which clearly stated  temp denture only as a stop gap and then a chrome denture.
This plastic one is driving me crazy, causing dozens of ulcers, falls out constantly and makes me vomit. It's half the length of my own teeth now my gums have shrunk with a huge gap between it and my teeth. Surely a course of treatment isn't finished until the permanent denture has been made and fitted?