Imperial gas pipes connecting to oven?

[teamboxer]

Hello

I have recently tried to have a new cooker fitted but I was informed that I couldn’t do so because I have an “imperial gas pipe” that attaches to my my current cooker. I was told it needs changing to a metric pipe.
Is this a complicated piece of work and how much should i expect to pay a gas fitter for the job?
I dont want to get ripped off.

Regards and thanks in advance

Adam