O3 are one of the two premier drysuit manufactures in the U.K., along with Otter. They prefer you to come to the shop to be properly measured so that the suits can be adjusted accurately.If they are lacking the confidence to offer it in the open, just not the sort of people I would feel confidence in ordering from.
I currently have an Ri 1-100 front entry. It is a very compressed neo suit. It is about 7 years old and is probably the best money I have ever spent on dive gear. I am in the process of getting the new trilam suit as it is lighter and has replaceable seals. My current neck seal is a bit loose and I am not in a place where getting that sorted will not loose me a load of diving.
Since I am st the other end of the country at the moment they are going to send me their best guess size of suit (or two) to try on and then to base any required adjustments on. Of course they still know the adjustments from stock from my last suit, maybe that makes it easier.
They are the kind of people you can ring up, or visit, and be talking to the actual boss.
Seaskin’s reputation here is not so good, they are at the cheap end of things. My buddy of the last few weeks has a pretty new one and has been having leaks past the zip which he eventually fixed himself with goo.They do have a nicer web shop though. If I wanted a cheap suit there is a good supplier local to me (when in London). No snazzy web shop but all the same options. Again a visit is important.
I think you lot are insane buying a suit direct from the U.K. with FedEx, customs and the like.