I would say if your not gas safe registered your way out of your depth messing with a condensing boiler. Have you had specific training on the appliance? Have you carried out performance tests to check air gas ratios, % and Co PPM? with a correctly calibrated flue gas analyser. Give worcester or British Gas a call im sure they can point you in the direction of the HSE and fill out a RIDDOR form for you.
Mr Hatespeoplewho are not qualified for the job in hand, May 2010