You can get a paypal which takes 3.4% plus 20p per transaction. This is what i use for Zealot. We have a 2S paypal set up using this scheme already.
Tax wise - this is not going to be an earner, just covering hosting costs and keeping Sorck fueled up with Relentless so he keeps coding new jazz for the site
There will be no tax on this unless it earns over £8,465 (i forget exact figure) profit, not revenue, per annum.
It should be registered to someone young, unemployed and not earning already (else it would be cumulative to current day-job earnings and be taxed)
[spoiler] Or not registered at all, its not for profit, its under the tax threshold, its not going into a bank account. If any cash is made, we can do some extra nice contest prizes or annual awards or have a few extra free kegs of beer at a 2S meetup!