Good shout! I wasn't thinking of him actually, but you're spot on:

2000 Bulls v Leeds at Murrayfield
2003 Bulls v Leeds at Cardiff
2006 Saints v Huddersfield at Twickenham
2007/08 Saints v Catalans / Hull at New Wembley

I was thinking of someone else, but also considered Old Wembley and New Wembley as different stadiums.

Was this the Captain Morgan trophy? If so, Warrington.

They were shy of shillings

Was it in the days of regular power cuts?

Correct in that it was Wire.
Warrington are the only team to have won the ITV Floodlight trophy in 1955/56 season, this is the only time the trophy was played.