wood burner - do I have to get a certified person to install it... and some other questions too.

[cupsnakes]

Is it a legal requirement to get someone to install a wood burning stove with a special certificate? Or can our builder do it. I've been told that it's not illegal to get it done without the certificate but that it would be beneficial if we sold the house. Is this true?

Also, I have just measured our fireplace hole and it is only 20" wide. Apparently there needs to be 4" each side of the burner so am needing an ultra slim model (the body should be no more than 12" although can have some overhang on the top). Am looking at Villager Puffin and a Stovax one which is designed to fit snugly in small holes (sorry, I couldn't think of any better way to phrase that ).

Opinions please!

the stove doesn't I think - but the chimney liner does have to be certified (we had a new one put in about 6 months ago).

we have the chimney liner and the builder is coming tomorrow to

1. repair the chimney
2. line the chimney with two flues: one for the gas Stanley range/ boiler in the kitchen and one for the wood burner.

It makes sense to get him to do it all but am not sure if it is actually legal...

we have knocked off the plaster around the brick hole - do you think I should get a mantle to go over (and just tidy the plaster round the sides) or get a complete fire surround and chip plaster off bricks up to the surround.
The rest of the wall will remain plastered.