Baker and Oliver grouped the Erica species into 41 categories and then those categories again into five broad groups: 1. tube-like flowers; 2. star-like flower mouths; 3. real heaths; 4. cloaked flowers and 5. flat or open-mouthed flowers (Ericas in Southern Africa. Published by Purnell).
This yellow one has tubular yellow flowers widening slightly in a translucent part near the flower mouth. A dark anther is just visible. The leaves and sepals are needle-like. E. nana or E. brachialis are possibilities.