Vintage BSA build - ladies

1.700c wheels basically = 28" as long as you go for larger width rims.
(also 29" rims might work wonders).
[this is despite they are both smaller than 27" rims.

1. you MAY be able to fit a modern BB, buy a cheap shimano enlgish thread and check, other than that you are looking for axles and bearings, and for that I MAY be able to help you out.
   Are both cups there? if so, then check that you can remove both of them, and then that makes life easier.
   
   

3.I believe Armourtex is somewhere around the £60 mark, but there are several threads which have better info than me.

1. Bike jumbles and local bike stores, especially if they are not chain bike stores.
   
   

Good luck.