Is there any way to tell Mark, I'm at home now and have tried closing them all off etc but feel the problem maybe bigger than I first thought! (trust this to happen when te in laws are away! ). Would flushing the system be a job I/we can do tonight?

I realy cant tell if the pumps working or not being honest, I can feel it vibrating but unsure if thats just the flow of water past the impellors??

Thanks again for all your help peeps! much appriciated!