PayPal charge 3.4% + 20p per transaction, so if someone pays you £10, you'll receive £9.46. There's no charge to transfer money from your PayPal account to your bank account.
Although PayPal can be a convenient way to pay (particularly if you want to offer your customers payments through your web site), BACS has to be the preferred way if poss, like Matt3 says, it's free!
BTW many people publish their bank details on their web sites, but I'm not sure how wise that is...?