All you can really do is check in the Postage and Payments section on the items you are interrested in and check that the seller is using Royal Mail or another delivery company you don't have issues with finding your address. If the seller has listed Other Courier you would have to contact them before you purchase and ask them what courier they are using, if it is Evri you can ask them if they would be willing to send it via Royal Mail if you pay the extra it would cost.
It all really depends on how rare the things you are buying are, if they are readily available there will probably be someone selling them using a courier company you are happy with.
