Right, I think I've managed to find somebody local that I can get live rock from in a couple of days. If I get my RO saltwater this weekend and set it up with my Juwel pump and heater for 24 hours, should this be ok? I still need to get hold of a protein skimmer though, I won't need this right away right?
That's good. If you can get it locally then the chances are you may not need to cycle the tank, provided the rock isn't out of water for more than about an hour. The die back will be minimal.
Half fill your tank with water and place in your heaters and powerheads. Don't fill it to the max line as you still need to add the rock and sand. Mix up your salt water to 1.026 SG. If you're planning on having corals in the near future, then you might as well have your SG at the right level. Its also a good idea to place eggcrate in the bottom of the tank, as it protects the glass from the rock.
Once the rock is in the tank, aquascape it until it looks nice. If you've seen a layout you like, then try for something similar. Once the rock is arranged, shut off your powerheads and pour in your sand. Doing it this way around ensures the rock is against the base of the tank, so it cannot sink into the sand, which might make a rock pile unstable and cause it to come crashing down and scratch or break your glass. I'd recommend that you leave at least an inch gap between the back/sides of the tank and the base layer of rock. This will ensure that your CUC will have access to all areas of the tank, so food and waste doesn't build up.
Once the sand is in, switch your powerheads back on and then add the rest of your salt water. I'd recommend that you get yourself two heaters. If one packs up, then at least you have another running to keep the water warm. If you don't have a refractometer, then get yourself some electronic scales. You can pick them up on ebay for £10 and are accurate to 0.1 grams. For every litre of RO, you add 35g of salt to give you 1.026 SG. I use an empty 5L mineral water bottle and simply add 175g of salt, then fill with 5L of RO water. Doing it this way saves so much time and effort, as you know that the salt is the right amount, as is the water. Mixing it up using just a refractometer is guess work/time consuming. The scales are THE best thing I bought for my tank
You won't need the skimmer right away, as its purpose is to remove organic matter from the water. Since your rock is being collected locally and should have virtually no dieback, and you have no fish pooping in the water, you'll be fine. You will need to get yourself some decent test kits (salifert) for Ammonia, Nitrite, Nitrate and Phosphate though, just to ensure you are ok to add your CUC and fishes.