Coming rather late to this thread (just signed up in fact), but as I have had a pellet boiler since Jan. 2013 my experiences might be helpful.
I have a Extraflame LP20 (nominal 20kW) boiler. This has an internal 70kg pellet compartment which is enough for 3 days in the depth of winter. We buy bagged pellets delivered on a 1 tonne pallet which lasts about 6 weeks during winter, at a cost of around £250 delivered. We get through about 4 tonnes a year for our 4 bedroom well insulated 1950s detached house.
First and most important point is, choose your installer wisely. Get recommendations and if at all possible use someone local. I did neither and am paying the price. I'm in NE England and the installer is in Merseyside, their service and support has been completely atrocious. The boiler has broken down twice now, first time was at the end of Sept. 2013, it took them 5 weeks to fix it (under warranty) and we had no heating for the whole of October. It broke down again the week before last and I still don't even have a date for a repair. The manufacturers (Extraflame) do not respond to my requests for help either.
Fortunately, I've found 2 companies who are working together to help me (massive cudos to The Centre for Green Energy in Hexham, and Piping Hot Stoves in Daventry for going way beyond the call of duty).
When it works (!) though it works extremely well. I replaced a gas combi and had a 250L pressuried hot water cylinder installed in the loft. The boiler feeds the radiators direct (no buffer tank needed) and is controlled by a programmable room thermostat. It takes longer to start up and produce heat than does a gas or oil boiler (10-15 mins) but otherwise behaves much like a conventional boiler.
Despite the problems I've had (entirely the fault of the installers) I do not regret switching to biomass. If this current boiler proves to be unsupportable going forward, I will replace it with a different make from my local installer.
Very noble of you ey86798 but a second installation after two/ three years is hardly economical costing, would you say a conservative £15k per installation? working out at over £10k per year plus fuel. The lowest price I found for installation was almost £20k which would pay my gas and electric bill for 10 years as well as the installation cost of a new ‘reliable’ gas boiler, giving the added benefit that the house would not freeze up when I have a 2-3 weeks away in winter, without the need to shift tones of pellets each year.