I have decided my Ideal Icos HE18 is beyond sensible repair cost, I
have chucked enough at it, so I am looking now for a replacement...

It needs to be a regular, vented system type boiler, but if possible
with separate boiler output temperature controls when heating the hot
water tank, to that when heating the radiators. Yes I presently have a
room stat and a water tank stat. I just like the hot water to be able
to be very hot 80C, I appreciate that is above the efficient condensing
range, but to heat the radiators the boiler output temperature need not
be quite so hot. 18+ Kw needed as present boiler is adequate. The
predecessor to that was around 32Kw, but some good insulation has made
that high an output unnecessary.

I had no input into the boiler make last time around, this time I am
looking to Vailant or Worcester/Bosch for a more reliable boiler.