what are the Best british schools to work in?

DESS and Doha College are the only schools that fully follow the National Curriculum. Other schools that are good and follow a more loosely based English curriculum are Compass and Qatar Academy.

I am familiar most with the first two, and staff seem generally happy there as they both have high retention rates. Both advertise jobs on their websites.

Sherborne.

Here's a list from the QL site http://www.qatarliving.com/schools

Not all British though.

Worth having a look at QP-related International schools in their community locations like AKIS, MIS, DIS etc