Yes thermostatic but the pump blends the hot and cold so water is hot or warm when it comes out !
10,5kw and it had been fitted on a job for 4 weeks cost over 200 quid and there boiler was renewed and they changed it to powershower and i scored it for 20 quid
bonus as well id allready wired the old one in our house with 10mm cable Im really not sure youre right on that one?
This one is from a quick google search (there are plenty more with more or less the same figures though) -
We use none of the above, so i like to keep an eye on how much my effort saves us ; )
(and we have a shower that you certainly dont want to open your eyes under!)
Also if your boiler breaks down you can still get a shower and even fill the basin from it speaking from experience and I second brightspark get a good 10.5kw

So what do you use?

)---- in the hot water system, my gas boiler is in the kitchen, the other side of the wall at the back of boiler, is the airing cupboard in the bathroom so max distance from boiler to tank is 2mtrs cold feed tank in attic above hot tank. Shower is 2mtrs from hot tank and bath is the same, but the other side of bathroom. I've had three combis, fitted two myselfand had negligible issues with any of them.
there still crap
my boiler just packed in after 30 years 10 years is about max life of a new boiler now and most need repairing before that mines an ideal standard heat only 7 years guarantee and apaRANTLY now do a one with 10 year
--- one hitch in my system , I now remember, I had a plumber in, to pipe the gas in to boiler. ( needed to be corgi reg) He let sand get in gas pipe from trench and it cost me two gas valves before I sussed it, cost me a fortune in wasted gas over a two year period 

with gas leaking through boiler, we where using as much in summer as winter, we were on a budget plan, which spread the cost over the year, so wasn't obvious only reason i sussed it was boiler lit up one day when I walked in back door, I heard it and thought---- eay up TIMER IS NOT ON! Why has it lit up ??? the draft from the door wafted/pulled the gas back down the flue and the pilot light lit it !!
So fitted new valve same thing year later. Stripped gas valve full of sand. Julian is that the Rayburn rescued from a wood somewhere?
Could you not use/make , a massive insulated hot tank as a heat store ?? rather than dump it ? I had thought about this for my waste oil burner, you can shut boiler off at night and run off the heat store.i still have not sorted out the heat dump for it



