If someone wants your bike, they will have it. Locks are a good detterent, but not bombproof. Krptonite do have great locks, go for a Gold rated lock and it should slow down any attempt to break it.
Ref lights; assuming you will be riding into the dark, you will need both 'be seen' lights and 'seeing' lights, especially for your country rambles which I assume will be on unlit roads? Any cheap flashing light with wide spill are good for be seen, Cateye do quite a few. IME (Cateye EL530-£50) was a waste of money as a seeing light. The light emitted was poor and is not good enough for the 10mile pitch black winter commute. I wont go into too much detail as lighting has been covered plenty of times before, but I would suggest research your seeing light and not waste money on poorer products. Good luck!