I'm not certain exactly what your question is. If you purchase an item listed in GBP, you'll see an approximate conversion to USD in the listing and at checkout. That approximation is based on the conversion rates at that time. The final amount you pay, however, will quite likely be slightly different, because conversion rates change several times a day, and Paypal/credit cards often use different rate tables than eBay does. You also need to be aware of any currency conversion charges your credit card may impose.
