Thanks for answering John, I can't take the cover off as it is screwed in and I really don't know how to take it off properly, but I don't think there are any water leaks as there is no sign of water under the boiler.
If you boil a pan of water and leave it, when all the water has evaporated there is a certain "tinny" smell - that's the kind of smell I get.
jennieflea
May 2009