There is a fantastic place in Lewisham http://www.westcombes.co.uk/home.php incredibly friendly with a huge range of antique and modern inserts.

Great, thank you!

Chesney on Battersea Park Road will answer all your questions.

Can anyone recommend a company that can advise on fireplace inserts? I am not even sure if that is the right term - we have a mantel and surround but only a fireback (?) rather than a cast iron grate. We don't especially want to actually light a fire in the fireplace but would like something more attractive than the fireback we have at present - but there don't seem to be standard sizes for these things so I'm at a bit of a loss. If anyone can recommend a good shop/supplier not a million miles from Balham I would be very grateful.