As above, go into a shop and play
You have an eye for a photo but need to work on your technique a bit, and if you really want to spend some money then an SLR would certainly provide a better tool and more options to play with
The main DSLR candidates for entry level are the Nikon D40 or D80, or the Canon 400D and others around that price bracket. You'll then need lenses, the standard beginners lens is approximately 18-70mm focal length, 18 is the wider end of that range, 70 is a light telephoto.
For the price range you've put up I would suggest you start out light, buy a DSLR kit (comes with the 18-55 or 18-70 lens) version of a nikon or canon entry level camera, this should set you back £3-400 roughly.
Buy a memory card, 2GB to 4GB is good. Each camera uses a different type so check what you need!
Then buy a circular polariser for the thread size of the kit lens (67mm for nikon kit, 58mm for canon kit i think, you'd have to check that). This will help you get some contrast into pictures like #1 by darkening the sky. You're only looking at about £30 for that.
Once you have these basic starting pieces, take a load of photos and think hard about what you'd like to be able to do - then ask us how you do it! There's enough experience here that someone will know what accessory you need to reach your goal
Don't blow all of your budget on things you dont understand.
OPTION 2:
Buy a brand new D300 with all that money. wait several months to get some more money. buy lenses and accessories
