I remember my first trip in GB - I was 14 at the time. My father did a bit of caving (held a level 1 ticket mostly to take kids into Flagpole on Portland). He was encouraged to be more of a caver to retain his LCMLA (funnily enough by a mendip caver) however attempts to do so was always awkward not being a member of a caving club. He attempted to join a caving club (East Dorset SS) but that folded around the time we tried to join which I guess was just bad luck. We and his friends from Weymouth outdoor ed center and Kingston Maurwood College (who also had LCMLA tickets) mostly repeated Swildons (sump 1 and back as he did not like sumps / ducks), goatchurch and prid with the occasional excursion to places like Lionels, Sidcot and Rods (no through trip in those days) as trips for pleasure until bored. Obviously trips to the usual places on Portland were regular too. I didn't go but I think they tried Eastwater once and hated the place. All of this was only during winter months as sailing took over in the summer. We meet a chap along the way who used to live in Weymouth and had done a fair bit of caving. He told us he would take us to GB but let him do the talking. At the time it all went over my head but the technique involved lying about being members of a particular Yorkshire caving club, hiding me in the car whilst this occurred in a Mendip hut (apparently the third person was meeting us at the cave), putting false details on 3 permits and then getting on with a bloody brilliant trip. The chap who took us was clearly well practiced at getting into locked Mendip caves!
After this my father tried to get legit access with a leader to Charterhouse (this was before the cave got bigger) and also Upper Flood and was told no it wouldn't be possible - Mendip club members only. He wasn't a hugely experienced caver, but Charterhouse and Upper Flood old caves would have more than been within his capabilities. He gave up with mendip caving not long after this but continued taking loads of kids caving on Portland for a couple of years. He also used Prid a fair bit during Dartmoor weekends. Unfortunately Dorset County Council then effectively banned caving on Portland so he gave up. I know that one trip to GB was the highlight of his caving career. I then didn't cave for quite a few years either until a work colleague convinced me to take him caving - one trip and I had the bug again. By this time I could drive, had job + money so got back into it and that was 10 years ago.
Access on Mendips needs sorting out. Being a member of one of the clubs it's easier for me than my Dad found it but a combination of the journey seeming to keep taking longer and then having to mess around with keys / leaders for so many trips I've got fed up. These are the two reasons for my recent renewed interest in the caves on Portland. No keys, easier journey, no politics, no leaders, just turn up and have fun.
I have to think of the many 100s of teenagers my Father took caving - they all enjoyed it but soon lost interest when when he explained he could only take them to a few rubbish caves on Portland, Goatchurch and Prid. If only they'd seen GB or a trip to sump 1 and back perhaps a few would have stuck at it.