PJAZ, if you do it, believe me, it's best to wear little clothing, like the guy in the picture above, rather than t-shirt, and joggers. I've tried both (actually, I only wore a loin cloth and trainers the second time) and was actually a lot better off with virtually nothing on. Reason being, the wet clothing against your body saps all the heat out of you. You freeze your bllx off waiting around at the start, but IMHO you're less likely to get dragged off for hypothermia before you reach the end.
You'll also get lots of scraps across your skin by not wearing much, but if the tv show captured the true horror of the cold, you'll appreciate it's a sacrifice worth making.
...and people think you're bonkers, when in fact, you're making it easier on yourself.
Only alternative to this is investing in some proper thermal clothing, but then you're really copping out and might as well be doing the summer event instead.