After a mixer shower refit the cold water in the same bathroom to the sink and bath will not come back on .I am thinking an airlock of some kind as I had to drain the hot water before the refit any help would be grand

I am thinking an airlock of some kind And I'm thinking that when you replace the shower valve you disturbed some minerals built up in the pipe walls and they're clogging the cold water inlet ports in your bath and sink cartridges. Where you made your mistaken was in not flushing out the supplies before you closed up the valve.
The solution would be to shut the water off and open up the valves one at a time. Check and clean the cartridge and this time turn the water back on to flush out the supplies before you reassemble. Good luck, Tom

Thanks for the quick reply, a true gent. I will be back on the job tomorrow and give this a go .as a friend just told me electricians should not touch water, I think I will take the advice , Cheers

a friend just told me electricians should not touch water, While that's true I wonder where that came from. Back tom you, Tom