The water tank in the loft is not filling up and the hot water is not vcoming out. I have opened the top and looked at the ball cock and pushed it and lifeted and no change. Rang BGAS services and they can not come out till Monday morning

Shut off the water to the ballcock and open it up. Remove the washer an d turn the water back on for a minute to flush out the supply and open ballcock. Did you have a strong stream? If so then reassemble and test. Ballcock working now? Good luck, Tom.