Benefit/cost might be there, but for a project costing 22B it would be sensible to study and quantify.
Perhaps more importantly, you learn the biggest hurdles so that you can address them. For instance, the UK doesn't want its power to be at risk from political instability (more than it is already). That risk can be addressed in part by working with the local population: perhaps you allow for co-located grazing so you're not displacing herders. Perhaps encourage joint projects that also provide local power so that Moroccans benefit from the project (beyond just the ones in power).
What about security? It seems a bit concerning if 8% of UK's power can be knocked out in a single attack. How would you address that?