Well, as you have the later coupe you don't even need spacers. I'm not sure if they fit under those alloys. Are you a member of any other forums? I am sure someone on Rovertech could confirm if they will fit or not.
If you are confident enough to change the pads on your own, you can change the whole brakes. You just undo the two bolts holding the carrier to remove the pads, then undo the two bogger bolts holding the caliper to the hub. If you are quick, you can undo the pipe to the caliper and put your thumb over the end to stop much leakage of fluid. Then get the MG caliper and quickly screw it onto the pipe. Dont panic but dont hang about or you'll lose loads of fluid. With the new caliper on, take the old disk off the hub which may be held on with one/two retaining screws. Put the new MG disk on and refit the caliper to the hub with the two bolts. Then fit the new pads and bolt up the carrier. top up the reservoir if required and repeat for the other side. You should only need to do the fronts and it wont knock the bias out enough to notice. With both new brake sets in place, you just need a friend to help bleed the excess air out. One fits a clear pipe on the bleed nipple on the caliper which leads to a container to catch the fluid, the other has foot by brake pedal. Open the bleed nipple and say "open" the other person then stamps hard as possible on brake pedal and says "down" lock the nipple shut and say "up" pedal gets lifted up and repeat three times. Check reservoir to make sure it doesn't get too low or it will draw air in system. repeat process two or three times and check firmness of pedal. Once happy, take for a test drive, hiting brakes regularly before attempting to drive at speed. if pedal not good, repeat bleeding and if necessary, bleed back brakes as well.
If you dont loose much fluid, you should not need much bleeding and you will have very good brakes. Just remember they will need to bed in so don't go braking too had or drive up people's back sides straight away.
It really is the way to go but if you are not confident or don't know how to change pads, get a garage to do it. If you live anywhere near Croydon, Surrey in UK, I will gladly help you for a couple of beers
