[satan]

Kev, i,m not a qualified gas fitter, but i have worked with one, it could possibly be the control valve,[ie, the knob that turns it on and off] a simple soap test [bit of washing up liquid and water] on each control valve should find any leaks, you may have to remove the fasia panel to gain access to them, failing that, get a professional to have a look. hope this is some help.

ps start with the most used one, as its normally the 1st to fail.