When you 1st start out (on the line or in the hangar) you won't have any certification priveledges - as your 'A' licence won't yet be valid.
In theory you also won't have any responsibilities, as the 'B' licenced Engineer who certifies your work ultimately carries the can - this would not excuse from any negligent act however.
You should expect +/- £20K at this stage of your career. The hardest part will be getting someone to take you on with no experience. I would advise you to bite the hand off anyone who offers you a job at this point, regardless of pay/prospects - as once you're on the inside your opportunities will increase tenfold.
After gaining your 'A' licence you will need to get company approval on whatever types your employer operates. This will involve your proving the relevant experience & under the current system your employer will need to provide you with documented training in those tasks.
The level of cover varies between companies, but you should expect something like preflight/daily/wheel & brake changes + cabin equipment changes.
Don't expect automatic progression to the next grade, but when you do - pay at this level should be in the high 20's/low 30's.
Guess you're at Northbrook? If so ask your instructors for contact details for the guys who have joined TCX this year, I'm sure they can give you the low down on the job as they see it.
Best of luck.