Stove
Assuming your ceiling is 3.2m, you need a 3.5kw stove (hxwxl)/14 (in Metres). Probably go for a 4kw one.
We've just changed ours and gone for one with a larger glass front, which seem much more efficient than our previous one. Squirrels are good – as are a load of niche brands, which will arrive shortly I'm sure.
We got ours from here: http://www.stovesareus.co.uk/
You will need to line the chimney – here are the details of a quote I've just received. It obviously depends on height, and how handy you are with welding gear:
7 metres 6 inch stainless steel liner 904 grade £ 67.00 £ 469.00
6-5 inch adaptor £ 29.48
5 inch x 2' stove pipe £ 30.00
5mm steel plate £ 30.00
steel angle £ 30.00
sand and cement £ 6.00
8 bags leca £ 9.80 £ 78.40
tile cement for hearth slab £ 10.00
consumables £ 10.00
Materials sub total £ 692.88
Labour £ 400.00
Total £ 1,092.88
VAT £ 103.93
Total £ 1,196.81