moving splint on old fire plase to house new gas fire

[tersmith]

hi all,
I'm looking at installing a new gas fire in my house, however as it was built in the 60's I'm told that the "lintel" (support of the chimney) is too low and needs to be raised.

Anybody able to recommend someone to do the job or have any rough idea of the cost involved?
I need to have the work done fairly soon so all replies will be gratefully accepted.

I look forward to hearing from you.

Tks in advance