No experience of actual Rayburn's but if a pilot light keeps blowing out it is usually down to the thermocouple getting tired and / or the pilot light getting partially blocked . Is the pilot flame yellow (weak flame) or mainly blue and is it hitting the thermocouple sufficiently or is a slight draught momentarily blowing it away ?
Other less common causes are a weak electromagnet in the gas valve or on room sealed appliances the appliance or flue is not sealed correctly allowing a draught to blow through or the terminal outside is not sited correctly.
Unlikely in your case but some of the later boilers had over-heat stats wired into the thermocouple circuit that could also cause trouble, going faulty which turned off the pilot light.
A rough test on a thermocouple is to blow out the pilot light and listen for the gas valve to click shut, if the delay is around 20 seconds or longer normally the thermocouple is ok.
Most pilot lights on boilers have a pilot injector fitted inside the pilot assembly where the pipe goes in that is the main cause of blockage Do not prick it out or you may end up with a massive pilot flame.
Pete
