Disputes with Paypal
I've got some free advice for anyone who needs to dispute charges at PayPal.
Firstly, if they direct debit you for charges that are invalid, simply go back to your bank. Under the Direct Debit guarantee the banks are responsible for fixing it. This is something that is highly regulated and will get fixed very quickly.
Secondly, if they close your account and try and steal money from it then you should consider the small claims court. Just write them a letter that basically says give me my money or I'll see you in court, include a deadline, and then if the deadline expires file at www.moneyclaim.gov.uk. Almost every time the company in the wrong will settle immediately and out of court. The key thing is to get the filing in (after a warning) because that is what genuinely scares the firm - they don't want convictions because they can get shut down by the FSA.
Finally, if charges appear on your bill and you don't have a direct debit set up, write to them explaining this, and stating that the bill is in dispute and won't be paid until the dispute is resolved. If they try to force you to pay, write again and threaten small claims action.
I've done all of the above at some point, and its all process that is worth knowing about.