You have to pay NICs as a UK employee. It's not just about pensions, NICs go towards schools and hospitals etc. Apparently. HMRC guidance:
When you come to work in the UK you have to register for a National Insurance number and immediately start paying National Insurance contributions in the UK on the same basis as other people who normally live and work here. Source http://www.hmrc.gov.uk/nic/work/ni-uk.htm
If at all, I do have to pay NI, I heard that you can legally avoid NI until just before the retirement age and pay it all at once.
Never heard of that one, sounds like a story from the ubiquitous man down the pub.