I'll be on holiday, which is why I'm not joining you all, but I thought I'd share the contents of an email I've just received this morning from Southern Railways, which nows shows that (on the whole) bikes are only banned between London & Gatwick.
Cycles
During the London 2012 Games, we are expecting our trains to be even busier than usual. We will welcome fully folded (Brompton style) bikes on our trains at any time, however, in addition to the usual peak time restrictions we have in place further restrictions will apply throughout the period 27 July to 9 September.
Non fully folded bikes will not be allowed on any Gatwick Express service, Mainline services between London Bridge/London Victoria and Gatwick (including via Redhill), on Metro routes or on the West London Route between Watford Junction and East Croydon.
Click
here for map.
So either get the train to Three Bridges and then cycle back, or cycle to Uckfield, and get a train to South Croydon, as that's outside the banned area.