You don’t say if this has been painted previously or you are starting from new. So, if repainting an existing facia it’s usually best to stick to what was used before. So if that was oil based undercoat and gloss repeat with the same.
For new work you’d be better off with an opaque stain rather than a paint as they tend to perform much better. Some are indeed water based and work perfectly well.
If you want a traditional gloss finish then Dulux Weathershield exterior primer, undercoat and gloss will serve you well. Compared to standard alternatives the cost is much higher but you save in the long run from increased durability.
A final note on the choice of black as a colour. Particularly for south facing aspects this should be avoided, if at all possible, since dark colours absorb much more ultra-violet radiation than lighter colours which are more reflective.
Thank you for your swift reply & advice, however, yes it had been previously painted with oil based paints, however this was in need of redec as it had mainly started to bubble & flake. I have now rubbed down, keyed existing paint work and under coated with Dulux primer undercoat X 1 coat, 1 X topcoat Dulux weather shield satin black. I hope this slows the requirement for a redec on this south facing aspect. READ MORE...
All the best