Hi Nick
OK, with this type, you need to remove the little circular retaining clips which are clearly visible in your images, grab hold of them with a pair of pliers and pull them out. The clips are attached to wedges. Tap these wedges out with a flat ended screwdriver and hammer. They only come out in one direction as there is a lip at one end, check for the lip first and then tap the wedges in the opposite direction to the lip, once both top and bottom wedges are out, the caliper should slide off.