Thanks for your replies, he did offer to fit an external one, but I can see an expansion vessel suitable for the Alpha240E available to buy online for £109. I will try another engineer and ask if they can fit it.
I have an Alpha 240E boiler that has stopped working. The engineer says it needs a new expansion vessel but he is not legally allowed to fit one because any parts have to be traceable back to the original manufacturer and Alpha don't make the parts anymore. Is this true? I can see the parts...