For those on a fulltime contract it really is quite simple: Part A: conclusive non-residence
2.4 In some circumstances an individual should have certainty that they are not tax resident in the
UK without having to take account of the connections they have with the UK. Therefore, Part A of
the test will automatically determine that an individual is not resident in the UK for a tax year if
they fall under any of the following conditions, namely they:
• were not resident in the UK in all of the previous three tax years and they are
present in the UK for fewer than 45 days in the current tax year; or
• were resident in the UK in one or more of the previous three tax years and they are
present in the UK for fewer than 10 days in the current tax year; or
• leave the UK to carry out full-time work abroad, provided they are present in the UK for
fewer than 90 days in the tax year and no more than 20 days are spent working in
the UK in the tax year.
Bullet number 3 is the relevant one.
If you work for BA and live in SA, or work for FR in Spain get paid in Eire and have a house and family in the UK then you probably have problems.
Live and work in the ME and meet the above requirements not a problem.
The above was lifted from the consultation paper, leave halfway through the tax year, fill the correct forms and the 90 days is pro rata. You need to be expat for 5 years I think to avoid remittance tax, might be 3.