Can the gas pipe can be run up to the loft between the false plasterboard wall.

In short no, a gas pipe cannot be routed through a cavity wall from the ground level to the loft. "The Gas Safety (Installation and Use) regulations (GSUIR) restrict any person from installing any part of any gas installation pipework in a cavity wall unless the pipe is to pass through from one side to the other. In this case, the pipe must take the shortest practcable route and must be fully enclosed in a gas tight sleeve." This is for two reasons one being the need to inspect the pipework for maintenance etc the other being that in the event of a gas leak that may occur in the void, there would be a dangerous build up of gas with no opportunity to escape, and obviously this is a safety issue because of the combustable nature of gas in a confined space would lead to a situation threatening to the occupants and the building. I hope this has answered your question, Homewood plumbing services.