hehe trying to think from memory, 22 or 24mm to remove the rear disc nut, and a 16mm or something similar to remove the rear callipers is all you need, and a screwdriver or something flat to wind the caliper back (rear wind back not push like the front)
remember when you remove the rear disc, there should be a little silver washer type thing goes between the disc and hub, sometimes this pulls off with the old discs and new ones arnt supplied arnold clark didnt fit one of mine when i bought the car on the condition it had new brakes all round and a month later they had a £400 bill to put it right lol)