Whatstove is an excellent site.
I've bought and installed three diffeent woodburners, and have used my inlaws' one as well. These stoves were:
- Aarow Acorn 5 (multifuel)
- Charnwood Country 4 (wood only)
- Burley Springdale 3 (wood only)
- Morso Squirrel (multifuel)
Once you've decided between multifuel and wood only, the key things are log size, glass size, efficiency, and flue size. The airwash system is also of note.
Of you don't expect to burn coal, then don't buy a multifuel. They can burn wood but not as efficiently as otherwise, harder to clean out, and you will need slightly smaller logs because the firebox is partly full of grate and ashpan.
The best airwash systems are those that preheat the air. My first stove (the Acorn) simply had a slider at the top of the door, so cold air would pass down the inside of the glass. This worked a bit, especially if the stove was cranked up, but nowhere near as well as on the other three stoves where the air is drawn through tubes or channels within the body of the stove and hits the glass already hot enough to vapourise carbon.
My latest stove is the Burley, which at 89% efficiency is claimed to be the most efficient in the world. It's installed in a new house that I am still building, so has only been lit a handful of times yet, but so far I am extremely impressed with it. The makers actually understand the principle of an efficient fire- get it hot, keep it hot, burn off everything and send only CO2 and H2O up the chimney. Hardly any ash, no blacking up of the glass, and barely visible whiffs of white smoke from the chimney. They achieve this with a dour stage burn and a very well insulated firebox- vermiculite on the sides and floor, and a double glazed door. The metal baffles in the stove then extract as much heat as possible from the fire before it reaches the chimney, leading to a flue temperature of less than 150degC.
The only drawback of a super efficient stove is that the low flue temperature can make it harder to draw on cold days, especially if the flue is oversized. Mine is attached to the recommended 5" twinwall and so far no problems.