Hmmm that really is a strange one
if you havent purchased anything , and they arent international... then i'm not sure where they came from unless they were RAOPK's , but then they should have had the senders info on the parcel anways (which they would have had to have done if they were international as well) . Have you double checked your ebay /paypal to make sure there is nothing you forgot about? did you happen to win/buy anything from ebay seller a.ramone recently? I ask this because another member here recently had parcels from this seller arrive that belonged to someone else, so they have got pretty mixed up with their buyers addys
Other than that are you expecting any mail from friends or relatives? (not pony/ Arena/ebay/paypal related)
TBH if there is no addy on there and you arent expecting anything else from the UK, then I dont think there is much you can do. If they were sent you by mistake, then whoever sent them will either realise it and contact you, or they will prolly end up making a claim from Royal mail for missing parcels