Advice/experience sought of installing gas/electric fires

[muffins78]

I'm just wondering if anyone can share their experience/knowledge of installing gas/electric fires in their homes please?

I'm in a flat, where the fireplaces are gone and am wanting to put in one, more likely a wall mounted fire in the existing chimney breast. An electric one would be an easy enough one to do I imagine, but what about a gas one? Would floorboards need to be lifted, if not, would a pipe of sorts be left exposed in the room? Would a flueless fire be okay, or more advisable to get one which needs a flue, but I don't know the work which would be involved in that.

Cost will be a factor too in terms of installation - but rather it done right and also get the right brand/model put in to provide good heat/effect.

Sorry for all the questions, I'm just trying to understand what would need to be done and what would be more suited to this flat. :) Thanks for any help :)