We have an oilfired worcester danesmoor 15/19 for HW and CH. The HW was only running lukewarm when the cold weather started until we had it serviced in Nov when it improved but has gone back to lukewarm again now so having to use the immersion for HW in the cold weather. It has also started to make a loud vibrating noise through the pipes when the heating thermostat switches the boiler off but the heating seems to be working well with all the rads being hot. Had some major work done to the house last year with 2 new bathrooms plus 3 new rads put in plus new HW cylinder in airing cupboard. The plumbers that carried out the work said we had 3 separate systems running off the boiler but managed to use the existing loops for all the work. Any ideas what the problem might be? 