As the Revenue issued a PAYE tax refund for 2010/11 you presumably completed a P85 departure form indicating that you expected to remain in full-time employment overseas until at least 5 April 2012. The refund arose in 2010/11 as the Revenue expected you to be regarded as not resident and not ordinarily resident with effect from 11 July 2010 which would have taken your overseas earnings out of a UK tax charge. On this basis the Revenue carried back the unused portion of your 2010/11 personal allowance and perhaps 20% tax band against your UK earnings which provided you with your tax refund.
Your plans appear to have changed as you are now considering returning to the UK without having been absent for a complete UK tax year (6 April to following 5 April). If your proposed early return materialises you will not break residence in the UK and will remain liable to UK tax in 2010/11 on your total worldwide income including your earnings in Qatar. From a UK tax efficiency angle, you should if possible continue working in Qatar until at least 5 April 2012 to avoid an unwelcome UK tax bill.
I have copied a link to the Revenue's website which details UK tax rates.
The Revenue will probably not have access to your end of year P60/P11D information, but will expect you to report this information to them.
Where my clients go and work overseas in a tax-free environment, I suggest that they maintain a UK tax fund from their overseas earnings to cover the UK tax charge that can arise if they unexpectedly return to the UK without having been absent for a complete UK tax year.
I hope this helps.