i have a warmflow combi which has recently decided to lose pressure gradually over 4-5 days,i have checked for leeks but cant find any and topped the system up.2 days ago we returned from shopping put the heating on and a couple of minutes later the the boiler went on lockout.the fire valve had shut off.i reset this and all was fine till this morning when the same thing happened again within minutes of starting from cold.are the 2 things connected or is the fire valve faulty.