Gas or electric fire in fireplace

[nubi]

I am going to renovate a 1950s 3 bed, new everything - plumbing, gas heating,electrics, insulation etc.
There is a fireplace in the sitting room I dont want an open fire or solid fuel stove, what kind of fire effect unit should I put in the space?
I want the look of a fire but not the costs associated with using it as a main heat source.
Are ther electric units that can give off some heat but are efficient and dont cost the earth to run?

Thanks in advance...