Longstroke

And it appears to be on flat tarmac with no evidence of the ground having given way under it. As the stabilisers weren't down I suppose they could have been driving with the boom up and turned too sharp, or just a really strong gust?

The additive is just a corrosion inhibitor to try and limit the amount of sludge build due to the dissovled oxygen in the water, exactly the same as you put in the rest of the central heating system. As regards antifreeze - it would be possible but you'd need an awful lot to protect 1000+ litres of water. Solar thermal on the other hand does have antifreeze in the system as the volumes (for evacuated tubes) are fairly small, but being stuck on the roof the risk of freezing is high! If you can fit underfloor heating it is a much more efficient way to make use of low grade heat - it will work with water down half the temperature of that needed for normal radiators. If you're (or anyone interested in biomass) near North Devon and want to have a look PM me.

We've installed a 20kW Log boiler and a pellet boiler with a 1500l thermal store - found a company selling them who were happy to let me install them myself with a plumber friend helping and then they came down and 'commisioned' them. The plumber has some industrial experience under his belt, possibly why he was comfortable with our system as there is also Solar Thermal, underfloor heating and a wood burner that just heats the indoor tank (300L) so it is a bit involved. The advantage of doing it 'officially' is that it should be possible to claim the RHI (renewable heat incentive) that the Government has carefully been putting off for the last 2 years - the reason we went official To meet the requirements for the RHI (via the MCS) it is necessary for the system to be a total replacement for all space heating requirements - i.e. you're not allowed to have an oil boiler 'just in case'. There was still a grant available called the 'Premium Payment' which is around £950 for a biomass boiler, while we wait for the full RHI to start - supposedly in summer 2013!! My fingers remained crossed. PM me if you want the company name - not sure if I should post it direct on here.

Think I managed to get some too. The guys donating kit are stars!