Forget this, talked myself out of it.

Most have high surface temperature (100 deg plus, only a few at 70 deg and could only find one at 45/55 deg C). Very limited options for large out put requiring more than one panel (most 300-600w). Once calculated on basis of low thermal wall insulation then output recommendations went up to 1.2kw, so not really low power and can't see it being cheaper than electric towel rail. Plus huge difference on costs from a few hundred to £800 or so, almost 3x towel rail costs. Not all IP rated either.

I would go for a fan and for comfort, even luxury underfloor heating, even electric and on a timer of course

You need the fan after

Won't it just move the air's water content to the wall faster? Simply blowing moist air about won't re-evaporate condensation. With warm air, the walls' temp lags air temp, so provides a condensing surface; with radiant, the walls and objects (you) get warmed, potentially even above air temp, so don't attract condensation.

In terms of reducing condensation, the point of a fan is to equalize the surface air temps and that is just one of the reasons MVHR works. If you use the open window approach all the obvious steam 'flies out of the window' but the the room cools, you shut the window and you a get a little condensation just where you don't want it - of course if you forget to shut the window you heat the sky..... Moving air on wet naked bodies is only good if 'exercising'.....Infra red work best in a bathroom for comfort but are a ridiculous price to buy, and run, it seemed to me and now to smudger too. Hence MVHR (or single room HR) seems best as low air velocity (ie on boost but is still relatively very low air speeds) but the boost speed will sort out the room before the condensation hangs around long enough for mould to grow. Of course this is why extractor fans are the only main stream solution - however if the hall or bedroom are lower temp than the bathroom (normally is so), or the bathroom door is relatively air tight and the windows are leaky, then cool air enters from the hall/bedroom and/or around the window causing higher risk of condensation in the ceiling corners and adjacent to the window frame and on the glass perimeter (esp if not warm edge) - so that's why HR is so much better than the next best choice of an extractor fan because very little diff in air pressure and HR inlet temp is no less than the bedroom/hall and may be higher.

That is the state of play as far as I can see from the multiple posts on here about such matters and my own personal experience/battle with mould.

The primary reason for the heating is to stop the mould - otherwise we could tough out the coldness ourselves (as we have done for 3 winters).

We've come to the conclusion we need to heat the house continuously in winter rather than off and on and avoid cold/warm spots (i.e. counterintuitvely not switching off rads in unused rooms as the moisture and warm air just 'flows' there and hence mould growing on cold walls). The green deal fiasco has also put an end to our ashp plans as well (doesn't work unless house is well insulated) and no manufacturer we spoke to recommended single room heat recovery in an old leaky uninsulated house. We don't find the 'moisture flies out the window - even in one bathroom which has two windows and hence cross flow it can be over an hour before visible steam has gone and even then we are left with moisture streaming down walls and a very cold room. And this is on windy exmoor.

Our windows don't have trickle vents and chimneys are sealed up with stoves /register plates so concluded the building is 'breathing' less than it should. The layout of building precludes PIV, as there is no central staircase and and we have an annexe as well. We know we have to address ventilation and have selected the following:

http://www.vapourflow.com/product/vapour-vent-passive-dehumidifier/ -
for vents in the bedrooms and living rooms

http://www.vapourflow.com/product/wad-b-warm-air-dehumidifier-bathroom-fan/ -
extracts in bathroom when it needs to, otherwise supplies slightly warmed air into the building (which will pick up the heated air from the towel rails and at least stop cold air from hallways etc coming into the bathroom).

plus extracts in kitchens etc.

If anyone has used vapourflow fans it would give me more confidence to order them as they are very expensive (and total is working out more than a PIV install).

We are also going to install a quantum storage heater (on economy 10) at bottom of stairs to try to maintain a minimum level of heat and thus keep walls above 16 deg C and avoid walls developing mould.

I selected the Rointe as they were the only high output (aesthetically pleasing) tower rails I could find.

We do have a wet radiator system but its powered by a lowly 6kw amptec boiler so we only use it when we have cheap electricity but it will, along with the wood stoves which we use the most, boost temps when needed in the evenings or in the mornings.

Am I mad? (about to spend thousands on kit and having a wobble!)

Thats what the vapour flow does but without the heat recovery- provides continuous fresh air and only extracts when humidity sensor says it needs to (based on absolute humidity, not relative). It seems a clever unit but comes at a price. Our aim is to warm house to maintain 16 deg not switch heating on and off.

I had in mind
http://www.amazon.co.uk/gp/product/B004OFHOYW/ref=pd_lpo_sbs_dp_ss_1?pf_rd_p=479289247&pf_rd_s=lpo-top-stripe&pf_rd_t=201&pf_rd_i=B006Z96748&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_r=1DK2G2NFXKJ4EQGS2XG4
Delighted to see they're still legal (?)