Simpler, cheaper and infinitely more sensible would be to buy a
free-standing gas cooker. No fitting probems involved, easily re-sited
or replaced if necessary, just a single flexible pipe coupling
required, designed for the situation you describe.
Just because every other **** in the universe thinks all
kitchens/appliances must be 'fitted' doesn't mean you have to meekly
follow the fashion. It's not a very good fashion in any case as fitted
stuff tends to be highly obsolescent and expensive in the long run.

cheers

Jacob