Before i start, again, i would like to say a big thanks to all who have given me some great advice! Cheers lads!
So.... Well after a few months the boiler limped along with nice CH and hot water, then HW reverted back to hot to tepid again 30 secs hot 30 secs tepid.
So i finally got around to removing the HE for HW today. When it took it off, as i looked at the HE, the top left and right were black coated and the bottom left and right were nice and clean.
So i put some cleaner stuff in it and now the top two are pretty clean, not gleaming, but i would eat my tea off them now! I then flushed the HE for about 10 mins to clear it out, not a lot of black came out just a few flakes the rest seemed to just come out like discolored water. I re-fitted HE with new o rings and a bit of silicone grease on it and got it all back together. All in all job took 2 hours.
Ran the HW and it is a lot better, not hot piping all the time but doesn't seem to be going hot and warm so there is improvement, but not sure how long that will last. HW setting on boiler is on high just in case you need to know.
The thing is that after replacing the DVM (it was shot when you took it out of it's housing and turned it over), value kit, both sensors and cleaning the heat exchanger is there anything else that could improve the HW, apart from replacing the boiler which i will be doing once i hopefully have my kitchen extension started and finished later this year.
Also when i do the kitchen extension i will want to put in a bigger boiler so looking for recommendations to look for so i can get some idea of prices. Two mates have just had boilers fitted one a Baxi 40 GA and the other a Worcester 37 CDI and they seem to be happy with them.
I'm not sure on prices yet, so what makes are good?