worcester 240

strange faults showing up in last week , repressurise system everything goes fine 4/5 hours later all at 0 bar eventually boiler puts off pilot light refill and relight pilot all ok for another 4/5 hours excessive hot water use also drops the pressure ,strangely> did have a problem last week when filling system as full mains pressure went through and activated prv for 4/5 min till realised what was happening and got it switched off, pump now doesnt seem as strong and an awful lot hotter any ideas greatly received, meant to say its a worcester 240

prv is passing

expansion vessel needs checking / recharging