My mum is thinking about signing up to 3 * BG service plan costing £180 per year which covered all parts inside the combi boiler and all radiators,This was done over a phone call but they are coming round to do a survey.I have read somewhere on this forum but can't find it,I was under the impression the 3* plan do not cover heat exchanger and radiators or have I got it wrong.Beside the point ,is this worth having ?