As others have said, the Bigger One was definitely more than a rumour. The circles which appeared on the Prom were a happy coincidence - they never really lined up correctly with where a possible route could go.
If I recall there was talk about it breaking the height record again, which at the time would be 420ft of Top Thrill Dragster. It would have launched from BPB, across the street and onto the beach, before diving down slightly towards the sea and then pulling into a vertical climb, reaching a top hat and then returning to BPB with an airtime hill. The manufacturer would have been S&S with a seat layout similar to a 4D coaster/wing rider. This seat layout meant the ride would launch out and come back as a full circuit but along the same line, the return track essentially being above the launch.
There were quotes at the time from the Council and RCCGB, which although did not confirm the ride type, did effectively confirm that there was a large scale ride being planned. There was quite a bit of excitement at the time and a genuine belief if anyone would try anything like this it would have been good old Geoffrey.
Tragically his death probably also saw off the concept, although there were always doubts about how viable the scheme would be.
Personally I think it could have gone either way. If the technology was reliable enough to deal with the weather, it could have been one of, if not the most unique coasters in the world still to this day. On the other hand it could have been a massive white elephant if it didn’t work.