Decent electrical factor is your best bet - Wylex for one make them BUT check the dimensions (If they are Wylex then Screwfix stock them) - some of the oddball capacities are slightly different in dimension. I assume you have halogen lighting in your bathroom - one of the lamps failing probably caused an inductive surge causing the fuse to fail.

At the risk of asking you to suck eggs, have you swapped the lighting fuse with the extractor fan to check the fuse is the problem?

Cheers Guys. Will get down to local electrical shop.

Right, if you are not familiar and comfortable with electrical work at mains voltage then I would recommend the services of an electrician, it is difficult to describe electrical fault finding by text but basically get a multimeter and see where you cease to have a voltage - It may be that the wall switch has failed.

What I have seen happen is that the spring clips on the light fittings that connect to the two pins on the lamps fail after time and the fittings need replacement. Similarly check where the tails from the fittings connect to the wiring from the transformer.

In the long run it will probably be cheaper to employ an electrician than attempt repair by substitution which is the other option.

Finally I must remind you that since the adoption of part P of the building regulations amature electrical work (particularly in bathrooms etc) is prohibited - personally I dont see why a failed ships steward that made deputy Prime Minister should be able to tell me what I can and can't do myself but there we are.

Have any animals been having a nibble on the cable?

You really need to do an R1+R2 test on the cable and then stick 500V down it (Insulation resistance test) to check the conductors and insulation respectively. Disconnect the fan and transformers first!

Or call your friendly local Berlingo driving sparky. :-D