Sorry, maybe I confused things. To NOT pay any tax, you need to be out of the UK for a full tax year.

For example:

If you arrive in May 2006, you will need to stay in Qatar for a full tax year - April to April.

So, in this case, your 'tax year' would start April 2007, and end April 2008.

If you go back into the UK tax system earlier than April 2008, and you will be liable for tax on your Qatar earnings.

You are allowed to spend up to, and including, 91 days per tax year in the UK.

It's worth consulting the designated department at the UK Inland Revenue - which is called the Centre for Non Residents. They are much more clear and helpful than the poor sod on the general helpline!

Let me know if you need more advice.