Morning all

I know there's some very knowlegdable people on here so wanted to ask if anyone knows the rules for gas fire flues.

We want to put in a gas fire but where we would have to have it fitted there is only a between the outside wall and the fence of 500mm.

We've been told that you need 600mm minimum clearance and therefore need either a special flue or some air bricks which seem to defeat the object. Quite for the flue was over £1200

Do I have any other options ? Is that a good price if there aren't as that seems a lot of money for a fireplace or am I being tight


thanks