Gas pipe routing

I am in the process of purchasing circ 1900 semi and one of the jobs I am planning is to install a new gas hob in place of an existing electric hob, however, the routing of the pipe line to the hob is the issue.

The current hob location is on an internal wall (X on ascii art below)

External Wall

-----WW-----WW-- |B D D | | | W - window | X| | D - Door | | | B - Boiler D | | X - Hob position

---------------- Party wall

The kitchen walls are plastered masonry and the kitchen floor is concrete.

My main question is whether to run the pipe line round the kitchen wall from the boiler, raise it over the door and down to the hob, or to run the pipe under the floor?

If I was to run the pipe in the wall does it need to be sleeved and what sort of depth would I need to chase the walls to.

I am planning on getting a corgi fitter in to do the connection to the gas supply and the hob.

Thanks for any advice in advance.

Yours

David Surgenor