I can assure you as a UK FR permanent employee I pay UK tax and UK NI only.
This deal is only available in the UK and on a permanent contract. It is the only exception in the whole Company. Every other option is EI tax and the country your based in NI or the equivalent.
As for pension I pay £500 pcm and FR match it at the rate of £500pcm however I believe you can top up your contribution to a figure I am not sure of but £1000 pcm could be correct but FR only match to £500.
Bearing in mind I was in the Final Salary pension up until end of last year when they closed it down this is a piss poor substitute but I will take it anyway. Its £500 for free from FR and anything for free from this lot should be had.