Be prepared to spend a lot of time on your arse If you can find/borrow a pair of impact shorts, they may help your comfort, although I wouldn't bother buying some just for the purpose of learning - they may come in useful at a later date when you hit the halfpipe.
As said before, don't buy hardware until you're certain it's for you. There are lots of outlets selling decent gear, maybe even go to a large retailer (there are ones like Ellis Bingham) at most Snowdome/indoor slope places. Haggle with them for a 'package' price on boots, board and bindings, or find what you like in the store, then hit the interweb to see if you can get what you like cheaper online (that's what I did). You can get some good used items off eBay too (although I wouldn't really go for a used board). There are always good deals on last season's stuff, but getting a deal on this year's gear, as we start the season might prove difficult.
Have fun, I've been to Hemel a few times, it's a good slope to learn on.
And let us know if you're goofy or regular