Re: UFH recomendations
You could try the web for vacuum insulated panels, a sponge like structure wrapped in foil and then pumped empty. Expensive, but the top of the range when space is an issue.
Temp gauges (or thermostats) combined with the electric valves at the manifold are a must, but when going for a "open plan" layout then one of them would do for all the zone valves suplying the open plan room. Usually only about 20m2 are covered by each zone piping-layout.
The insulation should be good and the timber on top (the flooring) should have not too much insulation properties, the harder the wood the better the heat transfer.
The gas prices can go up sharply in the next few years, there had been warning signs during this winter and official warnings by the dino organisation IEA this week, maybe just a stunt to promote nuclear technology, but nevertheless.
So put at least the insulated piping and an empty duct for the electrics in place before plastering/flooring up to make sure that a fast, non-invasive switch to suplementary solarpower can be done rapidly. Calculate for a space for the tank near to the boiler ( about 1.8 meters in diameter incl. insulation and plumbing works) as well as it's weight on the floor. That is if you're not going already for it. Heat storage tanks can be used to buffer the heat output of the heating/UFH system, a buffer tank might help to reduce the start ups of the boiler and making it more efficient. So this buffer tank -once in place- can be used parralel as well for solar heat storage. Install as well insulated pipes for warm the water supply for the washing machine and the dish washer -the smallest diameter, 10 or 15 mm. One pipe to many doesn't matter, but a pipe missing will make a mess when installing it after you've moved in.
Go for the lowest output of a modulating boiler, UFH's are slow to react and a low output is just what is needed. 2 point something kWh is about the smallest in the market.
The insulation around the pipes should fit tighly, much of the pipe insulation material sold here is to large to fit, to insulate well. B&Q have the right material, have a look at it, take a sample piece of pipe with you. It will cost 10 or 20 cents more per lenght but it's worth it.
EPS is about 30% cheaper then PU, so if space is no problem then go for EPS boards.
I can't think of more right now, but feel free to ask again. Good luck.