Carl- it is quite a punt from palace, my mate cycles to me- Merstham- from Half moon lane and it takes him an hour, i reckon it is still another 30/40 mins to the start, at least you will be warmed up
A train to redhill will give you about 30 mins warm up / dorking will give you about 10/15 mins ride.
BTW Dorking is the name of the station- not a verb.