The last generation GM5 were almost the definitive English Ceilidh band - and will be considered even the more so after their dispersal in 1996.
The Gas Mark V of the CD Jump! sought to bring an eclectic mix of music into high energy whole, the result made for a some excellent tunes and a lively dance. With Guizers that music has fused, is more laid back, and appears with a greater swing - having a saxophone in the line-up has a lot to do with this. Gas Mark V were a worthy successor to the highly esteemed, but sadly demised, Ran Tan Band.
It probably was the definitive Ceilidh band for experienced dancers, ones who do not need a foursquare fixed beat to fit their feet to. Gas Mark V didn't necessarily give this, the rhythm is looser, and thus requires more thinking when dancing.
GM5 people are now playing with for Stömp and the new Saxophony and Chalktown
For more details and a more definitive history, Trevor Bennett has put together the Stories and Histories of Gas Mark 5 (now on the wayback machine).
Gas Mark V, 1988, Festival C2, Cassette only.
Gas Mark V, 1991, Regul02 CD, Regular Records
Gas Mark V, 1994, Regul03 CD, Regular Records