From Denham, by the time you have landed and then walked down to the station (and waited for the inevitably delayed Chiltern line train), you could almost be in Central London via the M/A 40 in a decent car (about £50) - which compares with parking at Batters.
1/2 way through - I've started to have nightmares about the 29 seconds from the OM to the MAPt at Stauning ...
h-r
