Thanks to StuRox for his suggestion about fitting 110 front brakes to the Disco, I've now ordered a full brake overhaul for the Disco - 110 vented discs at the front and new bog std D1 discs at the rear. I was going to flush the system with new brake fluid, but having looked at the calipers it was pretty clear that the nipples would have sheared - to say the calipers are a bit rusty is an understatement!!! So the brake update was needed sooner rather than later lol. So thats another £300+ spent in 10 mins lol. Thats front discs, pads, calipers, pad fitting kit, new caliper bolts and gaskets, rear discs, calipers, pads, pad fitting kit, caliper bolts and gaskets, plus a +40mm braided brake hose kit. I've already got some ATE Super Racing Blue brake fluid, so I just need a nice day one weekend to get the lot fitted!
Island4x4 were very helpful in confirming the parts I need, so I just went ahead and ordered the lot from them. They tend to be pretty cheap anyway so I'd probably only save £10-20 by shopping around.
So thanks again StuRox - I'd have just fitted the std parts if it wasn't for your post.