TIRES! When you say 28" tires there are at least 3 different tires in 28" size!!!
Old english roadsters used a 28x1&1/2" tire,Dumpster Diver has a good set to sell.700s are also called 28" tires,and some call M/B 29ers 28" tires.Need to know which rims you will be using?If your lasing in a coaster brake like a new departure my guess is your using a 36 hole rim---and I bet it's a 700 account almost all English rims were spoked 32/40,and don't fit american hubs
Any of the tubes made for 29ers,or 700x28(or wider)will work in the English Roadster tires with no problem--get a set at your local bike shop.Be sure and tell them it's for a wide 700 not the skinny 700X20s---sam