I have found the Installer sheet of paper and it is an Ideal Acos HE 24 model installed October 2007. The letters L and F appear and when I press reset it will run for a bit with a small letter c under the heading burner. But then I will find it has shut down (until a later attempt). I rang Ideal boilers and they want £299 to come and "repair" it ! Is this a straightforward issue that a local boiler engineer may be able to fix. I have no idea where the manual is for it. Thanks for looking.
Sounds as though the Ideal people know exactly where the problem lies. If they can guarantee to repair it for a fixed fee, it may well be the best choice. Some random engineer may make one visit to identify the fault. Order the part, wait for delivery and then return to fit it.
Two visits and a part will leave you no change from £300.