Route and timing
Luton is around 120 miles north of Brockenhurst: M27 to M3, a stretch of the M25 anticlockwise, then up the M1 to junction 10. Roughly two hours and ten minutes when the roads are clear.
Like the Stansted run it depends on the M25, but it leaves that road sooner, which makes it the more predictable of the two long northern routes. The M1 section is rarely the problem; the M25 between the M4 and M1 is.