Rights if no room for cycle on unreservable train

[jopsuk]

Out of interest, can participants take their bikes on other lines in Sussex to London (if they cycle to such a station)?

Here's the policy as it stood in 2010 (I imagine it'll be much the same).

Essentially, the answer is "no".
On the idea of using class 325s- I wonder how many bikes you could get per carriage? You'd need some sort of check-in/check out system I'd reckon, and would want a passenger service (possibly dedicated) to go with each 325 departure.