The UK is quite northerly. It is at about the same latitude as Alberta, Canada. Morocco and the Western Sahara are at the same latitude as Florida.
In the UK you have a yearly irradiation of about 1000 kWh / m2. In Morocco it is closer to 2450 kWh / m2. This means that the same panels produce over twice as much power. Once you are planning utility-scale solar, it becomes a bit of a no-brainer.
Besides, the vast majority of solar is already located in large arrays due to economies of scale. 50.000 local arrays isn't even an option for utilities. And even if you were to build 50.000 local arrays, each of those arrays would have to be 210 kW - that's close to 600 panels per array!