* its a bit difficult trying to get a handle on the movements of the 4 in their last 24 hours - and whether they (or some of them) stayed near Luton on the Wednesday night.

at a minimum though, it seems that the bus bomber actually stayed in Dewsbury on the Wednesday night and left for london on the thursday morning:
"When he left his home on Thursday morning, with only a few hours to live, he had told his parents the was going to London for the day with friends." LINK

* maybe they all spent Wednesday night in w.yorkshire:
"The friends, three aged 30, 23 and 19, had travelled from Leeds, West Yorkshire, that morning having picked up the mobile bombs, probably from a house in the Burley district of Leeds. The gang is thought to have driven down in two or three hire cars." LINK