Riccardo: I have been and know of other foreigners who have worked for African companies - it is possible but it is not your right and you have to bring to the table something that company wants ie. a rating, a language, maturity/command, contacts etc. If you don't have it get it.
Try contract companies as they don't need to apply for work visas if you are based outside the company's country of reg.
As with most things in life it's all about timing.
But I believe no hard work is ever wasted so I'm quite sure you will get 'that' job. In the meantime use this time constructively and when you get your call be prepared to make sacrifices/compromises.......we all do.
As for your english; I've flown with guys that couldn't string a conversational sentence together and others who were practically dyslexic it never affected their ability to do a perfect landing and make safe judgement calls.
.........and don't forget however hard it is in Africa there is a LOT more competition in UK - we have very highly qualified pilots from all over the world (EU and commonwealth) vying for jobs.
Good luck.