The Solent Plastics ones claim to be the only completely sealed ones available in the UK. They also state the cases are completely watertight unless submerged, and are airtight. Assuming you put stuff in them in a dry atmopsphere (not always a certainty) and check in some silica sachets, that's possibly the best bet.
Overall, mind you, I would always suggest the absolute ideal is to never store stuff anywhere cold and/or damp in the first place. There is always some moisture in the air, but as long as the temperature stays reasonable, it isn't a problem. Seal stuff in a box and then put it somewhere that gets close to or below freezing point, and there will be some condensation. There always is, and it can be an issue if stuff is left for too long.
If there really is no option, then one of the indoor storage unit type places may be the best bet. They're dry and not overly cold. As someone has already mentioned, the downside is that they're not cheap. If you need to store stuff for an extended period, it can get very costly overall.