Which finish would be best for a natural look exterior oak table?

I bought a large oak dining table from a warehouse sale thinking it would look great on the patio/back garden. On further inspection it appears that the legs and outer frame are solid, but the two inner pals that make up the table top are infact oak veneered chipboard. If i don't seal the top well, it will lift and spoil in no time. I've spent the afternoon sanding off the horrible orange/yellow finish an taken it back to it's natural colour, so am now looking to apply something to protect it that will be flexible, won't darken or change the wood's natural colour and remain as true as possible to a natural sanded finish. I'm in the uk by the way, so it's going to experience a wide spectrum of weather conditions.