Tom, you have to understand something. Here in Qatar people are somewhat categorized. There are a lot of people from developing countries, who live very different from people from other countries. They are paid according to nationality, therefore the gap can be very big.
The people that say you will be fine, or even say your package(lol) is good, are usually from developing countries.
Qatar is relatively expensive, especially if you want to keep the standard that you are used to in the UK.