I don't know if you still need advice as i've just noticed that your post was ages ago.
SpR - Specialist Registrar, essentially second in command, the most seniour after the Consulant.
SHO - Senior House Officer. what you become after 1 yr of post graduate training.
I'm afraid that i'm not sure what all those other acronyms are, and I worked in the UK!!!
And no, I'm pretty sure that clinical attachments are not paid. Clinical attachments consist mostly of observing as there will be lots of junior doctors and med students who will usually get priority in terms teaching/training. Of course, if you are really proactive and are attached to a good, helpful firm, then you could get lots of hands-on experience.