Tier 5 GAE? Tax rates, and applying for tax exemption

My sponsoring institution has informed me that I may be eligible for a tax exemption on my L1000 monthly research allowance (visit and allowance have a duration of six months, starting April 2014).
I am seeking advice on a couple of questions...
(1) What kind and amount of taxes should I expect? and
(2) How can I initiate the application for this exemption from far overseas - e.g. by email - prior to travel at the end of March?
Any / all advice is most appreciated...

you are only taxed if you earn in excess of 9440 in a calender year , so 6months x 1000 = 6000

but have to register to NI and pay NI which would be around 2.7 per week