I actually did Denham-Shoreham a few weeks back, and it took me all of 35 minutes in the air (at 110 knots). I could have taken advantage of the helilanes but decided against it as I'd not flown them before with someone who had and it would have increased my workload to an unacceptable level.
I went north, round the top of the zone, south missing White Waltham's zone to the west, then over the top of Farnborough at 2400' to avoid their ATZ, then direct to the Steyning gap.
Dead easy, even with the high controller workload - a total of about 4 radio calls to Farnborough, and a lovely day to boot.