True, but there will also be a trickle down effect, as well as a burgeoning middle class.
Trickle down dosen't really work in this situation, as exporting grain dosen't really require amuch profesional involvement. It requires capital and semi-skilled labour.
The middle clas, if it does grow, will be built totally speratly to the agricultural land owners - it will be the managment of the growing uurban industries that forms it.
Thinking about the effects of continuing fee trade, and the types of technology that will be accelerated by the additional wealth and people.
The biggest one is containerisation. Cairo, as terminus of two major rail lines is going to be an immensely busy port, and the other ports in the Empire and Britain will be immensely busy and overcrowded. This makes Britain the natural place forfr this too be developed.
Late's say then, that some bright spark working for CtCaAR (Cape-to-Cairo and Associated Railways) invents containerisation in 1926, as the problems for transferring from the trains to the ships are becoming significant and expensive. This catches the imagination of someone senior in the company, and he pushes it, both within the company, and to his friends in CtSHR (Cairo to Singapore and Hanoi Railways). They have contacts and investments in shipping companies, and the ball starts rolling. The most important proves to be the owner of the Tilbury docks.
Containerisation becomes standard on both railways by 1930, and Tilbury grows massively to become the new Port of London, serving the massive and growing London-Cairo trade. This will be associated with industrial disturbances, as the dockers were notoriously militant, but Tilbury is mostly a new development, and the other unions' members are too content to come out in support. The resulting crash in the cost of shipping (by a factor of 40) is seen by other shipping companies, and containerisation gradually becomes the norm, over the next decade. The Germans embrace it enthusiastically.
This will give free trade, and the economy in general, a massive boost. Most importantly, outsourcing now becomes viable. By the end of the 1930s, Britian should have shifted into an economy based on skilled labour, thanks to the education programs. Unskilled labour will be becoming very expensive in relation to their output, and so all the conditions are met. If India is still peaceful, and Diarchy has been a successful model, we are likely to see a significant number of unskilled jobs leaving Britain and going there. If this happens during an economic upswing, possibly the upswing that will come after the downturn associated with the disruption caused by containerisation, it should be possible to do without too many protests.
This will further increaes economic growth, particualry in India and Egypt. Cairo in particualr will be become the center of a triangular trade:
Raw-material
Congo->Cairo->India,
Low skilled industrial produciton, textiles, etc
India->Cairo->Britain
High skilledly goods, machine tools, factory equipment
Britain->Cairo-> India