I have looked at this thread
http://tinyurl.com/3ef9x
and others on Google Groups to try and answer my questions, but found
nothing definitive.

I am renovating my house and plan to install a completely new gas-fired
central heating and hot water plumbing system. The renovation includes a
loft conversion, so I want to avoid a system that involves header tanks. I
am assuming that this means a sealed system for mains pressure hot water.

The heating system will be underfloor heating (typically 55 deg C), plus
supplementary heating (probably conventional radiators at 80 deg C flow) for
when the weather turns really cold.

I would like to install a water softener (not a water conditioner) that is
compatible with a sealed system and a few on this newgroup have recommended
an ion exchange type. Does anyone have a personal experience, successful or
otherwise, with a water softener and sealed system that might influence my
choice of softener and boiler. What makes of these do you have?

The main supply water pressure at my property is 2.8 bar (measured one
February lunchtime). My wife and I have three small children, one bath, two
showers and three toilets as well as a frequently-used washing machine and
dishwasher. With the old oil-fired vented system we used to have, our water
bills show a consumption of about 200 cu.m. per year.

A difficult question I know, but can any expert out there recommend a
"dream" boiler-type/storage tank/heat exchanger so that I could start to put
together a system specification that has a good chance of working? I would
rather err on the side of buying good quality equipment than a cheap
solution.