on the oxfizz thing: i genuinely think it's really sketchy. they sent an email round my departmental mailing list (i'm a dphil student) asking if there was anyone who was willing to work for two weeks, for free, basically on a coaching camp where rich kids' parents pay thousands. i had a look in their finances and on the charity commission website and so on, and it's ambiguous how much money actually ends up going to charities - it's very easy to say "for every kid who pays we support a poor kid to get a free interview", but given that it would have been me, doing the interviews, for nothing, it's ambiguous where the rest of the money goes.
i got the distinct feeling that this has been set up by some random oxbridge grads who want to take advantage of people's goodwill, having seen the number of people who volunteer for access schemes and target schools and so on. there's nothing to stop the three directors (or whatever they call themselves) paying themselves an enormous salary, stating that it's a company expense, and giving away the remaining pittance to whatever charities.
sorry for pissing on everyone's chips a bit here, but it's the kind of thing that makes me feel genuinely uncomfortable, and the tokenistic "oh well it's cool we let some poor kids have some free interview practice" doesn't seem like it's sufficient to make up for the problematic side of it. if anything, i feel like it undermines the work of the access scheme a bit - they put so much work into saying "honestly guys you don't need coaching we can identify your real potential", only for a bunch of people to say "oh no wait really you do need coaching, do it with us so we can make our cv look awesome"