Yu find out from where the leak is coming and fix that.
Soap bubble test on pipework and joints and around taps
Soap bubble test on jet of suspect burner would suggest whether it is the valve.
Spares
http://shop.electrolux.co.uk/category/Moffat
http://www.espares.co.uk/browse/at1092ma707/cookers-and-hobs/moffat
XXX
December 2016