Flexicom Hx ? that's not a combi that's a heat only boiler you must have a hot water tank !! if that's the case more than likely one of the controls in the airing cupboard has stopped working
Carl do yourself a favour get a Plumber in for couple of hrs to do your valves and replace the 2 Red handle valves in your airing cupboard for full bore leaver valves, don't forget to put inhibitor back into your heating system
Just to add to your information lots of houses built in the 70s in and around Saltash (Cornwall) same builder fitted with outset fire, but when people asked about new fires BG condemned the flues, to close to the finished plaster the wall up through the lounge and above bedroom got so hot you...
looks like there used to be a BF boiler at some time, Proberly find that window never had a opening on that side and new DG windows fitted and the flue has been overlooked typical of DG company's But you need to get this fire problem sorted if its pulling in smoke
Well depending on how long you have been doing this job, you could see more and worse, I've seen things that would make your hair go white, B4 CORGI and the need to report everything, and still come across some very bad sights ,
Dish washers tend to be cold fill what model is it ? did you get any instructions with it, if not go onto bosch website you should find the information you require.
Its my understanding that HSE like to collect information and build up a file on the offending person Don't think much gets done for a one off reports, unless something serious has happened , Explosion etc.