I can just about make out the R clips through the pad retaining pins Chris so looks like Girling to me. You'll need a pair of long-nose pliers and a pin punch to remove the pins.
The top R clip is fairly eay to see, camera angle doesn't help on the bottom one but i've circled the top one and where the bottom one should be.
I'd give it a wire brushing first to remove any loost rust, apply a little penetrating fluid to the pad retaining pins where they go through the caliper then pull the R clips using the long nose pliers.
Use a pin punch on the inboard end of the pad retaining pins and drift the pins out using a hammer on the end of the punch. The punch should be as close to the size of the pad pins as possible but slightly smaller - not so small as it dishes the end of the pin and not so big that it gets stuck in the caliper.
Remove the anti-rattle spring (the H-shaped spring that locates under the pad retaining pins) after the pad pins are out, withdraw the pads and anti-squeal shims (if fitted).
My idea of the G-Clamp may not work as well as i first thought as it looks like (from your picture) you have pistons in both sides of the caliper, it's not a single piston sliding caliper as i thought it would be.
Remove the rubber dust cap (assuming it's survived the past 30 ish years) from the bleed nipple and give it a wire brushing followed by some penetrating fluid around the nipple. Find the correct size ring spanner to fit the bleed nipple (often 8 or 10mm) and put the spanner on followed by the one-way bleed valve. Slacken the nipple by ~1/4 turn and use either the pad spreader or long screwdriver or similar to ease the pistons back into the caliper. Sometimes it helps to temporarily refit the thicker pad in between the other piston and the one you're working on to prevent that one popping out.
Once you have the first piston fully in, temporarily fit one of the new pads in front of it, remove the old one from the other side and push that piston back in too then close the bleed nipple.
Remove the temporarily fitted new pad so you have access to both sides of the disc for a file. Wedge the file in so it's acting on the edge of the disc where there will be a slight lip which you can see easily on your pic. Use a long handled screwdriver between two or three of the wheel studs to rotate the hub/disc while holding the file against the edge of the disc to remove the lip, repeat for the other side of the disc.
Clean the surfaces of the caliper where the pads move in them and now grab the new pads and the file. Go round the metal edges of the pads removing any burrs, drips of paint etc that may cause them to stick in the caliper. Apply some copper grease to the metal backs of the pads and on the edges where they make contact with the caliper - the old pads should have witness marks to indicate where they are.
If it had (or the new pads come with) anti-squeal shims, press one onto the copper grease on the back of the pad and smear some of the copper grease onto the mating face of the shim that meets the piston. Insert the pad into the caliper and repeat for the other pad.
Clean the pad retaining pins with a wire brush and smear copper grease on lightly. Fit the lower one first, ensuring it goes through the anti-squeal shim holes as well as through the pads - push it home finger tight. Make sure the hole for the R clip is at an angle you can easily refit the R clip.
Now refit the H-shaped anti-rattle spring, locating the bottom of it under the lower pad retaining pin. Now repeat the pad pin procedure above with the top one, ensuring you catch the anit-rattle spring under the pin both ends - a small screwdriver helps to push the anti-rattle spring down to make life easier.
Once both pad pins are in, refit the R clips, pump the brake pedal a few times to ensure it is firm and the pistons have moved in to take up the clearance.
Repeat all of this for the other side and finally once everything is back in place with new pads, check and top up if necessary the brake fluid reservoir under the bonnet.
If you find the pedal is spongey (not springy, new pads will make it springy until they bed in) then it would be advisable to bleed both rear calipers. There shouldn't be any air in them but it sometimes happens.
Other than that, give it a road test to make sure the back brakes work (reversing then hitting the brakes will show them to be working or not) and go and have a well-earned coffee/tea/beer/whatever - delete as appropriate.
I don't think i've missed anything, i'm sure others will soon pipe up if i have though!