If someone pays by paypal it is received into your paypal account immediately. You can then transfer the money to your normal bank account which takes 3 working days. I believe it is free to transfer more than £50 but there is a charge for under that amount. What i normally do is sell my stuff and keep the money in paypal until i think i'll need it, then just transfer as a lump sum. This way, if i going to buy something from ebay the money is already in the paypal account, and doesn't need to be funding from my current account/ credit card and this just saves me transferring back and forwards.
I usually post by royal mail, collection only will make your auction restricted to people in your local area, and i personally don't bother with this at all. If an item is heavy, make it clear in the auction that they can either pay for delivery or collect and then that way you don't eliminate any potential buyers.
Royal mail insured delivery is best, a little bit more expensive, but at least you can prove an item has been delivered if a buyer falsely claims that it was never received
