Thanks for all your comments. The fan behaves the same way if I set the fan going then remove the energy saver and have no bulb as it did with it in, so I guess the high impedence of the energy saver is the issue.
Bernard: I'll give your suggestion of inserting a relay a go when I get a...
I'll try experimenting with a few other brands at some point then, unfortunately all I have in the house are identical as they're selling them for 10p each in Homebase at the moment!
Yes, I've put the old bulb back in now and it's back to turning off after around 5 minutes. There are two bathrooms in the house that both had the same problem, so I'm pretty sure it's not the fans themselves going wrong.
Hi,
I've just changed my bathroom light to an energy saver and found that my fan doesn't go off. With the old filament bulb it usually stayed on for about 5 mins before clicking off.
I'm guessing that this is to do with the the fact that filament bulbs allow current to pass through them...