You accountant is probably using maybe in case HMRC tryto use the 3 yr work contract guideline a recent addition I believe to the guidance notes.
If you have been paid from Qatar that should make it clearer, if you have to claim it back cos you were paid PAYE in the UK that may cause you some problems as it's harder to get it back from them.
Remeber though that if you get another job over here or anywhere you have to start the full tax year eligability thing again as it won't be continuing employment.
Also remember you are not paid Tax Free you pay local Income Tax. The rate of Income Tax applied is just 0%.