In reply to OneLifeOneHeart:
Another vote for stalking sale rails - especially worthwhile if you can get somewhere with lots of big retailers in a row that you can pop into such as covent garden. That's how I got my >250 coat for <100 but I guess depends on sizing.
Like most things, fit should come before features - an expensive jacket that's not quite right will always bother you, whereas you can put up with a more budget one being not quite as swanky if it's comfy in the right places such as wrists and waist.
Another reason not to shell out yet is not knowing exactly what you want at this stage. Would be a pain to buy something expensive that doesn't really work with your layers. Lots of people seem to go for a couple of layers with a very lightweight tiny packable windproof/showerproof over the top, instead of a more substantial shell.
Clothes are a bit of a cost barrier to starting any outdoorsy pasttime at the beginning, so just get whatever's good enough for now and then upgrade later. I've got quite a few heavily discounted branded bits from go outdoors online (collect in store then try on) but then I'm a size that seems to hang around so am lucky. It also helps not caring about colours - if you want to coordinate a snazzy outfit that is harder on a budget!