yep tried pulling the switch back while tap is running and boiler fires up . So it looks like I need my missus to stand there doing that while I have a shower. lol
The diverter valve has been damaged perhaps by an incorrect application of mains pressure.
I have heard of the flow restrictor being damaged by connecting backwards and its also possible the diaphragm could be damaged by the same thing.
I dont recommend it but I suppose you could use a rubber band to hold the switch on but remove it before turning the water off. The boiler should be able to manage itself but as its under guaranty I would urge caution.
You was right from the start Tony it was the pipes round the wrong way. I take my hat off to you and thanks again for your input. After you had said it still must have been the pipes I cut out the back of the cupboard so I could trace them right through to the boiler and the cold feed was going to what should have been the hot out. I called the guy and he came out ( I was impressed it was 6pm sunday evening) and switched them back apparently my father in law said they was twisted to start with and when the fitter finished they was straight so thats where the mix up happened.
Thanks again to all who offered advice but big thanks to Tony.
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