Ronnie and his company were outstanding. Their approach is to assist by phone first rather than have a call out. In my case we needed a call out and they were there the next morning and 1.5 hrs later all fixed.   The cost of the works was very reasonable as they are NIBE approved.  Never use a non NIBE approved company - I know from bitter experience that you will be charge 400% markups on parts   I highly recommend Ronnie and his very experienced team. 