Why are my radiators and water luke warm?
My gas cooker is also not working properly, when I turn the gas on it lights the ring but there is hardly any flame, is this linked?
Its natural Gas.

Sounds to me like your not getting enough gas to work these devices. I would have a professional check the gas pressure to make sure your getting enough gas to operate these devices. Maybe your pressure regulator is not working properly or there's something in the line blocking it from going through properly.

Is it LP or natural gas?