HAHAHAHA I was the one answering my own questions here, no one helped one bit. I told you lot it was a y plan. I worked that out because of the components in the system, and the fact it had a v4703 mid pos valve. All I wanted to know was whether every system needs a pump, I thought it might have been under their floor or something. I still didn't get the answer, someone even said "a y plan won't work without a pump". I wish I'd never asked to be honest. Thanks though for all the really really useful advice.