Hi Stealth,
My first caving trips were in Burrington but when I moved up to the bigger wetter systems (Swildons first) I was still caving in a boiler suit, old clothes, home made lamp and a builders helmet. It didn't kill me, but I certainly appreciate modern clothing and reliable lighting.
You will feel the cold if you get wet in the stream and I would suggest that you save any wettings till the end of the trip. This will mean that your group can experience the more exciting aspects of caving in a wet system, but without too much discomfort.
There is a route I regularly use in the upper parts of Swildons which starts easy, gets progressively more difficult and finally ends with a wetting. The route is somewhat contrived and takes in most of the upper cave, but allows bypassing any parts which prove too much of an obstacle for anybody.
As an added bonus the route repeats very little passage way and is never more than 10 - 15 minutes easy caving to the entrance.
If you want a guide on a Swildons trip I would be happy to help, just pm me.
Les Williams