After a test ride i've settled on the new Dawes Graduate which i tried at Station Cycles in Cambridge. Its the only step-thru steel town bike with a 7 speed hub and non back pedal brakes that i've come across. Also i think it will handle a bobike mini front seat and a hamax plus on the back. Plus its a dawes frame so i'll feel confident that it'll handle me and mike and stuff.
I'm waiting for my voucher from cyclescheme, so once it arrives i can get the bike and i'll let you know how we get on.