This is a reply for later readers with the same problem: i have the same model boiler. Note my fix requires removal of the secondary heat exchanger for cleaning and this can be a bugger to access, you probably shodul also have spare washers ready in case they also need replacing. Anyway the cause of my hot water problem was scale/debris in the secondary heat exchanger was preventing the dhw heating up enough. Had to remove the secondary exchanger from the boiler, flush it, then fill it with kettle scale remover and place it in a hot water bath (eg a pot of water on the stove) for 20 mins but careful NOT to allow the water bath water to mix with the kettle scale remover fluid inside the exchanger), the descaler i used worked best when it was hot, then tipped it out the descaler, flushed through the exchanger (lots of debris came out). Anyway i repeated the whole cycle a few times until it flushed out clean and then put it back in the boiler and hey presto normal rate of nice hot water again! Note if you are doing this then it may be worth also replacing the air vent (£5 from toolstation/screwfix). Maybe also clean the water pressure sensor which is the part covered by a rubber boot (with a cable coming out of the top) next to the red emergency release valve, you need to unscrew the pressure sensor and just scrape inside the hole where the water goes in because if youve got a blocked/dirty heat exchanger then your going to have build up in pressure sensor as well. Hope that helps someone (if anyone still has one of these models that is!!)
LS80Tuser, March 2013
