Where did you park up?
I hate the clock watching if I use the park & ride or take the bike on the train, so been looking at leaving the car at Cambridge North station and cycling in from there.
My Modus Operandi for getting into Cambridge is via the St Ives Guided Busway.The last time I took the bike in the car to Cambridge, I left the car in the Tescos superstore just south of the Cam and cycled in from there. It's free for 3 hours.
I usually park in St Ives and ride into Cambridge. I now usually fold the Brommie up & take the bus back.
I don't know how much the car parks along the Busway are but St Ives is free.