Gee what a really helpful post kirkgas, but please don't waste your valuable time again.
I simply want to know what type of pipe to lay, and when the time comes, I will use a properly qualified engineer to hook things up.
Useful answers appreciated, unhelpful not.
Hey man! I would personally ring NASA headquarters for the safest advice, don't play with safety, it is beyond your capability! you need highly skilled specially certified people to pop in to give you an advice how to lay a pipe that will be carrying gas to your future cooker!
You know it is a rocket science! so I would definitely call NASA scientists, and since they are 5 hours ahead of us, when you get home late you should still be able to catch them whilst they are still at work.
You don't need any advice, just your instinct and bear safety of heat from the underfloor heating, obviously keep the pipes as far away as you can and I would certainly not bring them any closer than about 6 inches from the nearest element strand, but even if you are not going to use the cooker as yet, lay your pipe in, but don't connect the feed end to gas until your cooker arrives, then get a Gas Safe Engineer (ideally from NASA) to connect your feed pipe to the gas supply, also make sure your hob must be plumbed in using the copper pipes all the way to the hob terminal, with an isolating valve and again it should be kept very close to the wall as many oven do not have sufficient depth behind to allow for isolating valves with larger handles.
Personally I would run the pipe in the floor using a small duct, which can be made out of timber or plastic trunkin and then the rest concreted over, but provide wooden supports to the pipe so that it is floating in the middle of the duct, and have the duct such that any ingress of water from any spillages can escape and not pool in.
Further more, remember to have any joints in the pipe run under the floor tested for any leaks before cementing over the duct or covering with tiles, as you won't be able to get to them once your tiles are laid, pressure test them for any leaks, how you can do this is quite easy, use manometer and some pressure and leave the pipe under test for a few hours and you should not loose any There should be atleast 1" thicj layer of cement over the duct cover carrying the gas pipe inside, on top of which you can lay your tiles.
And you can make a sophisticated home made manometer using a length of clear plastic tubing bend in a U shape (halfords sell some, or even B&Q) and stick it or glue it to a stiff board, and filled with water and leaving the upper ends open and one side connected to the pipe under test, and pump some air pressure in the pipe under test using some home made adaption, raise the manometer water level to about 6" of water in height, and mark it and leave it for a few hours and the level should not change wahtsoever, bearing in mind the temperature change in the room may cause small changes, so measure the level at the same temeperature.
By the way, its up to you if you trust NASA scientist, they did get it wrong on the Chellenger!