I have a currently disued fireplace in the lounge,
which I want to have a gas fire fitted to, but
I have a few questions first.

The fireplace has a brick chimney, I've scraped out
the dodgiest of the mortar and replaced it with new stuff
(It's not what I'd call a perfect job though). There
are some sound but unnattactive tiles around the front of the
fireplace which I'd like to change.

Can I just tile over the existing ones, or would it be better
to remove the old tiles first? Do I need special heat-proof
tiles?

Also, I've noticed that in winter I do get some dirt coming
down the chimney when it's windy, though not a huge amount.
Would I need to get the chimney swept before I had a gas fire
installed?

There's already a gas point for the fire. Thanks for any tips.