as Sym0n said - 1st thing 1st - buy boots! and not just off a website, goto a shop and get the fitted. Sure, once you know what make and model suits your feet then you can go and shop around the net, but if it's at an independent shop like Subvert/ss20/etc you should support them (in an ideal world). Boots should feel snug, almost to the point that if they were trainers they would be too small so try on LOADS (don't just settle with 1st pair), listen to the shop-assistants and let comfort and support guide you, even if they're bright pink and have rainbows on... With sales I'd think you could get some decent boots around the £130 mark.

I'm a little taller and a good stone more and happy on a 156 in a dome (and on a mountain), so would look at 155's as a starting point.

you can certainly get some good buys atm:
Atomic Pivot 156 - £161
Stepchild Latchkey Ripper 156 - £195
Signal Park 154 - £210
Omatic Boron 157 - £175

just from a quick 5mins looking around

all the boards I listed are well reviewed and worth a look, infact here's another:
Atomic Hatchet 156 - £175. if you can stretch your budget a little more then a K2 WWW, Forum Chillydog, Salomon Sanchez or Capita Stairmaster might be worth a punt (if you can find them) but some might be getting a little too soft for roaring down a piste if you go away with it.

from £500 I thought this:
£130-150 boots
£110-150 - bindings
thus leaves about £200 for a board with possibly a little left for pants, etc.

if you can find yourself the Whiteline's magazine buyer's guide then it might help a little... Was released in Oct tho Basically it's a quick paragraph or 2 about all the main boards released in the season (something like 250 boards were in it this year) - I've got mine within arms reach, so can quote anything for a specific board that you're interested in (don't fancy listing all 250 tho ) But, despite being a board test, practically all 250 are glowing - as they even said themselves, there's practically no duffers out there from the main manufacturers.

As for makes, as long as it's a make you see in a shop like TSA, Snow and Rock, SS20.com, etc then it's reliable (just avoid those that can only be found on eBay...). Much like football teams, cars and practically anything, some prefer one make and slag off others while you get the exact argument from someone else for the reverse products. Equally some prefer the big boys (e.g. Burton) while others the underdogs/trendy-alternatives (Capita or Never Summer) and purists occasionally slag off the oldschool ski manufacturers that have moved into boarding (Atomic & Rossignol).

for board reviews I'd suggest looking at http://www.shayboarder.com/ for a start - pretty honest (if you can get past the Never Summer loving). and if you're really struggling then the Good Wood awards might be a good starting point:
http://www.shayboarder.com/2009/08/shays-take-on-the-2010-good-wood.html
basically the main boards of the season are tested by a load of ppl, they pick their favourites and thus a list of what a load of ppl think are "good wood" for the year. Much like my comment about reviews earlier tho, what they think is good might not be ideal for a beginner and/or dome (but those on that list tend to be those that sell well and thus you can probably re-sell easier if you want to get shot of it).

That Atomic Hatchet I linked to in this post is generally regarded a one of the best boards for the price and ideal for a beginner and intermediate rider, so will last a while (just a shame this year's gfx aren't half as good as last )

as for bindings:
Union Contact for £120 pretty good deal that one.

tbh, Hatchet with those bindings could be a good setup - but, like most things, personal opinion doesn't equal fact...