tricky -- you will be aware that you really should call a corgi man in.
low pressure or cutting out could be due to a number of reasons
first and this will be difficult for you
can you measure the gas pressure at the appliance when the appliance is on??
if not then I suggest you go no further
because if you are unable to measure the pressure then it is unlikely you can go further
obviously make sure main gas cock is fully on
without further detail I can give no better advice
dave broadbent, June 2007