One of the best ways to make sure you are dealing with genuine sellers on Ebay is using their feedback scores. A lot of overseas sellers have latched on to the "UK Seller" idea and regularly post union flag images as part of their item. I would say that if an item appears to good to be true / over half the price of other uK sellers and they appear to be a UK seller, check the feedback. Even the power sellers with 1000's of feedback often have over 99% good feedback if they are reliable. You often find the overseas sellers who are not geniune never get to power seller status or really high volumes of feedback. Feedback is always key to how well the seller has/is performing. That is the best method to avoid a scam in my opinion.