C# - I continued to use your advice and have been fiddling with this system for the last week. We had an electrician look for faults and could find none. Last week I noticed that the pressure has dropped by a bar so thought that there must be a leak somewhere. To cut a long story short and ignore the bit where I nearly killed my husband, a small leak was discovered coming from a rad without a thermostat. One rad also needed bleeding. Bob's your uncle...problem solved. Let this be a lesson to all. Make sure the rads are not leaking especially if you have an unvented pressurised system, bleed the rads regularly, top up pressure and life should be worth living again. Thank you C# for the clues.
Helen
March 2011