The boiler is now fixed. The pump was very stiff which has now been freed up. I guess I will have to change it eventually.
Thank you both for your reples.
The low water level led is illuminated. I have topped up the water pressure to nearly 2 bar and switching off the boiler and then on again still does not work.
Presumably a switch is preventing the water pressure being registered, if so can I over-ride it to at least get the boiler working...