Schmied (1991) notes

Schmied, J. J. (1991). National and Subnational Features in Kenyan English. In J. Cheshire, English Around the World: Sociolinguistic Perspectives (pp. 420-432). Cambridge: Cambridge University Press.

This is the last of three articles in the Cheshire's collection of articles, English Around the World.
Some interesting information:

• a difference between East African English and West African English is the pronunciation of the u in but (Schmied does not specify the pronunciation of each).
• vowels differ from RP vowels much more than consonants (which is true of the difference between most dialects).
• there are fewer vowels in Kenyan English than RP.
• there are differences in East African English depending on the speakers' L1.
• there is a tendency to say words as they are spelled. So, few letters of the written word are left unpronounced (calf and half) even in contractions like let’s (p. 428).
• there is some resistence to RP because of covert prestige among East Africans.