If not Ipswich go to Stowmarket. It's 30 odd miles of quiet roads and 2 years ago there were 3 of us with bikes that got on the 11.11 to Cambridge. It was empty.
Not according to their special terms for the day, only Ipswich or South of there if there's space.
Best bet is to ride it, 30 miles through flat countryside... Or find somewhere to kip Sunday and come back Monday, you can get a train to liv St for 9 mknday
Can you catch the train from Norwich?