Fastflow, before you have a strop.
I think people want to know why you'll be charging people twice over.
First you say its £12.50 to use the site but you want donations to buy it.
what would usually happen is the fees the players pay would go towards buying the site/paying for the site and or fields etc.
I think you need to keep a calm head.
work out what the first outlay is
IE owning the field
bunkers
netting
etc
then work out from that what to charge players. that way if your owning the field the £12.50 fee could be eradicated altogether.
if you keep a calm head and ask the question people with the know how will help.
trust me I'm trying to get a field going too