I used to use a 3mm surfers' sleeveless wetsuit with a couple of light woolens ( no fleeces in those days ) and overalls over everything, plus wetsocks, and that worked pretty well for most things.
4mm jacket for really wet crawls and passages like the Kingsdale Master Cave entrance or Swildons' round trip
I tried various plastic waterproof oversuits but found that tearing was a problem, especially as I did most of my caving using ladders.
''the stopes soared beyond the range of our caplamps' - David Bick...... How times change .... oh, I don't know, I've still got a lamp like that.