As I understand it, if you are domiciled in the UK exemption from income tax liability would require you to:
a) Complete a full tax year outside the UK
b) Spend less than 183 days in the UK during any tax year
c) Spend less than an average of 91 days per year over 4 years
If you are posted abroad (non-UK) then there does seem to be scope to pay local income tax and get a partial UK rebate.
If, however, your dets are such that you meet all the above criteria I would suggest:
a) Killing your boss
b) Doing a runner
c) Killing your boss and then doing a runner
If you fancy a bit of light reading on the subject then may I suggest IR20; just the ticket for those lonely 9 month dets:
http://www.inlandrevenue.gov.uk/pdfs/ir20.pdf