With a half decent program (I use Navbox Pro for UK VFR) you can do the route and get wx and notams in 10 minutes, with everything printed out and ready to go. Anytime in the past 10 years there has been no reason to do things the hard way, with the stupid circular slide rule and all that crap.
Obviously a decent GPS is a must if you want to make things work smoothly.
Getting the plane out of the hangar etc etc is another thing altogether
But circumstances on that vary a lot; some people have huge hassles while others just phone the hangar firm and the plane is out on the apron ready to go. And everything in between.
I think that most UK flights of 1hr or less can be driven in the same time, or less. There are some exceptions, mostly caused by UK's perverse road/rail network which tends to radiate out of London.
There is a particular trip I do fairly often, which takes 1.5hrs to drive, mostly along the A27 etc with some slow bits at the ends. I fly it whenever I can; with the drive to the airport (15 mins) and a taxi at the other end (10 mins, £10) it takes exactly the same amount of time in total, door to door (1.5hrs). The airborne time is just 15 mins however, and it is too short to boil off any water in the oil, so (given that I always have passengers) I take a detour around the IOW to streatch the airborne time out to 30 mins
An IR, or an IMCR for UK flights only, does help but you don't get full use out of it without a capable aircraft.