Hi could someone please tell me what the 3 wires are and do that go to the fuses beside the battery on a big turbo escort cosworth.

 

Those three wires are the power feeds to the fuse box inside the car beneath the steering wheel

 

if they are two red wires and one red and blue wire then
the red and blue is main supply for the ignition switch and ignition relay.
one of the reds via fuse 25 goes to the radiator fan relay
the other red from what i can gather from the wireing diagram is power supply for for the horn via fuse 20 and hazzard.