If its people from Barnsley specifically and Barnsley fans, I saw them at Oakwell earlier in the season and there were just a few chavs in burberry, literally about 10 of them. My mate whos a Forest fan was into this type of thing a few years ago and he and a few others shoved a Gillingham fan in the Trent and has been guilty numerous times of causing trouble inside the ground and now has a 5 year ban (which isn't long from being up).
Theres normally a bit of a skirmish occasionally, United v Wednesday for example but 90% of the time theres never very much trouble that I can see or am aware of whether inside or outside the ground.
Some teams are pretty notoious (Cardiff, Millwall, West Ham) but its certainly not the 80's anymore.