I am having the same problem at the moment although with a different make of uplighter. If you look at the metal ends of the small fuse with a magnifying glass you should see the value. Mine is marked T2.5AH250V. Whatever the value of yours, you should be able to get one in a good electrical shop or a place like Maplins. Take the old fuse along with you so that you get the correct size. They are smaller than a plug fuse.
Bear in mind that something caused it to blow so the replacement wmay do the same.
Hope this helps
Dennis
March 2009