Very good points 'Ski. I know mountain bike stuff is (generally) hugely overpriced at the best of times, but so many people just don't realise that proper, decent quality stuff that'll actually stand up to the kind of abuse it'll get on a trail costs a lot of dosh.
That £300 bike above is actually bang on for the money, especially when you consider a decent set of forks alone would typically START at that.
http://www.tredz.co.uk/rockshox-bike-forks <-- e.g., and I deliberately didn't use Fox as an example, as they're even more pricey.
You don't *need* top spec stuff to enjoy getting into biking and when all's said and done pretty much every single part can be upgraded as/when it either wears out or you get into it more.