ok I got it working. It was the fulcrum arm, must of jammed when i ran the hot water put drop of WD40 on it and pushed it in with some plyers seems to working fine now. Thanks for your help :)
got home yesterday to a very cold house. The central heating has packed up on my Vokera Excell 80SP, the hot water is working fine & the water pressure is at the recommended 1.5 bar, any ideas, Thanks