The brief answer to this is "yes, but not very many."
There was one official regiment of African American slaves who fought for the British. They were organized in Virginia and were called Lord Dunmore's Ethiopian Regiment. Around 1100 slaves joined the regiment, with the promise of being freed after the war. It may, however, not be all that correct to say that they "remained loyal" to Great Britian. This is more of a case of them going with whichever side seemed likely to free them.
We can see this from the fact that a larger number fought for the Patriot side. Somewhere close to 10,000 slaves are believed to have fought in the Continental Army. Most of these slaves were also hoping to be freed after the war.
So, there were slaves fighting on both sides, hoping to become free after the war. Please follow the link below for more on this.