Cheers I didn't really want to go back, but for a fiver I guess it's money and time well spent if it saves the BB. 2 tifosi's later with threads miles off BSA, glad I got a campagnolo one now.
I suppose if you're going there anyway, it wouldn't hurt to get it faced in case you use an external BB in the future: money spent on frame prep is never wasted.
Getting the threads chased would be a good idea if you've mangled a BB in there previously: a modest inconvenience compared to trashing another BB.
If you're using a cartridge BB you needn't get the shell faced, it's only necessary with separate cups to ensure they're parallel.