MIMH is right. Rental is very expensive, at least 5-6k for 2 bedroom, away from Westbay area. Further out will be cheaper. Westbay will be more expensive so it depends on where you will be working. If not nearby your accomodation, then you need to factor in the transportation costs as well.

Food is expensive - but if you avoid eating out often and just keep to once in a while, you can save money by cooking and get foodstuff from cheaper supermarkets.

And yes, no income tax as yet. They wanted to introduce it some time ago but guess that didn't get off the ground.

/Edit:Your recent post from your research appears to be closer to the mark. But like I said, it depends on many variables - eg. your home country's market rate, is this offer a better one? Your UK salary cf cost of living there, etc.? Suggest you factor in the accomodation which is a hefty chunk of one's salary in Qatar.