The reliable way to hire a tradesperson

Local water company fitted a meter to my property, obviously they shut the water main off, since then the cold water tank that supplies my non-combi boiler won't fill, the float valve is operational but the tank won't fill and so I don't have hot water. I've tried the airlock fix of back flow through the kitchen mixer tap but it's not worked, any ideas?

I’m going on holiday for 10 days. I’m turning thermostat down low so radiators won’t heat. Upstairs and downstairs separate thermostats. Should I just turn hot water tank off upstairs so water doesn’t heat up? I don’t want to turn the whole heating system off as it’s all timed bits complicated to redo it

If there is water leaking from my external water stopcock, is this my responsibility to fix or the water company?