I have a greenstar 32/50, problem: If the boiler has been "off" for more than 4 hours, when it comes "on" it fires up for about 7 seconds and then cuts out. Wait about two minutes, press the (now lit up) reset button and it fires up and will run all day without a problem. Again, when it is switched off overnight and and comes on about 6 hours later same problem. The boiler was recently serviced and a new oil pump and ignition controller fitted (£250.00) Prior to that the boiler started puffing brown smoke from the flue (soot build up in the baffles). I do'nt really have a lot of cofidence in the engineer ( he didn't tighten the nuts on the baffle plate sufficiently for a start) Any ideas anyone?