Well on trains say to cambridge, I've been able to have it in the carriage with me, but trains back to say newcastle require storage in the cabin which requires a ticket. However there were only 3 bikes on the way there and only mine on the way back, so i guess you could try and wangle your way on. but for longer trips, just ask for a cycle space! it's free after all and you can do it while you order your ticket (even online).
Well on trains say to cambridge, I've been able to have it in the carriage with me, but trains back to say newcastle require storage in the cabin which requires a ticket. However there were only 3 bikes on the way there and only mine on the way back, so i guess you could try and wangle your way on. but for longer trips, just ask for a cycle space! it's free after all and you can do it while you order your ticket (even online).