Please be aware that when PayPal ask you to set up direct bank funding of your PayPal Account (usually when you reach the £200 sending limit) they are actually setting up a Direct Debit to take the amounts you spend on purchases out of your account. Therefore, although you may THINK the money is leaving your account immediately, it may take some days for the Direct Debit to be completed and cleared through your bank account. Please be aware therefore that you may end up paying returned Direct Debit fees to your bank, particularly if you are unsure as to your current bank balance. I picked up £245 returned Direct Debit fees in ONE MONTH in this way and although I sucessfully had £200 returned by my branch, I would hate others to make this mistake.
In short, if PayPal ask you to set up Direct Bank Funding, read the terms and conditions CAREFULLY and UNDERSTAND what you are agreeing to, it is in fact a variable Direct Debit not Direct Bank Funding and items will be paid for by PayPal, even if your bank account can't cover the payment.
Hope this is helpful.