You need to apply for a licence with 7 days of arriving in Qatar. There is a form that needs to be signed by your sponsor giving you permission to drive. I had a Canadian licence, and was able to get a Qatari licence automatically with only an eye test. You will need 3 passport size photos.
You can drive on an international drivers licence and that is easy to get in Canada for a small fee at your local CAA office.Also it is useful to have an international licence for renting cars in many countries. You would still have to register within 7 days of arrival. I think a UK licence is also on the list of countries which automatically qualifies you for a Qatari licence.