Some extensive web searching has not helped me find this bird I discovered in my travels. They were flitting too fast to get a decent picture, but here is the best description I can obtain from memory:
Dark Grey from their head to their back. Their wings looked black but, as I said, they were flying about. Throat and breast were pale, probably white. Belly and vent were bright yellow. Their beak was a similar shape to the Purple Sunbird. They were taking nectar from bushes bordering a house which had small white flowers.