On inspection found that they dont in fact have a gas pilot light at all. They ignite electrically when the heating is turned on the flu fan runs and when the correct air pressure is detected it creates an electronic spark which fires up the boiler. My fan had packed up but I found a company on the internet which still makes new ones and they are so easy to replace.
The company are called Abcotuk and are a very small outfit but they sorted me out!
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