Electrics - somthings blown!

Yesterday, my central locking stopped working - it stopped working on both doors, so i looked into fuses - good start as the 15a fuse had blown. I replaced the fuse, locked and unlocked a couple of times - it worked but then the fuse went again. They are old fuses, so i thought it may have been a dodgy fuse, time to replace again, but this time the fuse didn't go, however, the central locking doesn't work, now the elec windows don't work either. Does anyone know if there is a master fuse which may have blown, or a relay or somthing?

Any help would be great as I'm in the process of selling the car, typical it all happens this week eh!!!

I'm useless at leccy stuff, but there another fuse box under the hood of the Landy its a big black box, on the drivers side, if you still have your book with you, check your book and see what duz what