When considering switching to biomass for domestic properties the first thing to do is get a green deal EPC (Energy Performance Certificate) carried out on your home. The report will give the energy rating of the building and the RHI payback is based on this figure. Reports are carried out by a green deal approved independent assesor, there is a cost for this survey please.
Then a suitable space to house the boiler and associated equipment needs to be identified, as the biomass boilers are larger than ordinary gas/oil boilers.
New micro pellet boilers are now available when space is an issue, these are more like your traditional boiler sizes, these boilers are also ideal for new builds, contact for more details.