Third one is correct.
First one isn't correct because "that/which" should have been used instead of "who". Second one isn't correct because Electricals 4 Africa is a collective noun that requires singular verb.
In the third sentence relative clause is reduced to -ing participle. (organisation that/which refurbishes--->>organisation refurbishing)
P.S. I'm not a teacher, yet. I'm studying to be one.
- For Teachers