I have rang them and they have told me if it is an internal problem there is a £67 call out charge. They have advised me to ask neighbours if they are experiencing similar problems before proceeding but neighbours are at work at the moment. My house is on a main street and there are no overhead cables, some cables out the back but I'm pretty sure they are BT phone lines. Can you think of anything internal that would affect different circuits, simultaneously, without tripping RCB or individual circuits? I can do without paying their call out charge if I then have to get a spark in to sort something internally.