the Waterworks will be out in full flood next year as the QE2 intends to go for a drift down the Thames a la Georgie Porgie 1 in a barge with Her Most Honourable Companies of Watermen and String-Pluckers in attendance.
Others have already suggested the 1812 overture. It's the dramatic finale which gets used for firework displays. Picking this up from 40 seconds in seems to roughly fit with your description:
Yes, it certainly was, thanks to one and all who answered, just put it down to my ignorance of classical music that I didn't recognise it from your clips.