The Bottom Bracket should be a 68mm English thread, very few if any bikes now have Italian threaded BB's, and the term British is extremely uncommon. You would need to work out the BB spindle length, or go with the easy route and get a HT2 type / Ultra Torque BB, where this isn't an issue. The stamped marking on the bottom of the shell have no relation to the dimensions.

For the headset, from the pictures, it's a fully integrated one, you still have the bearing's installed, all you should need is to take the numbers off these, they should be printed / engraved onto the races, with this info, choose from your budget buy and fit, a good guide to headsets is here http://www.hopetech.com/webtop/modul...ETS2011Web.pdf and here http://chrisking.com/headsets/hds_inset

For both, get yourself a good set of vernier calipers, with these you can check the dimensions for what you need.

Any good LBS should also be able to give you this info if you take the frame to them, but would only ask them if you intend to buy from them as well.