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Cobalt drills are great if you use them on a machine at higher speeds with lots of lubricant. They’re not really suitable for hand tools, they’ll chip and snap easily.
Drills specifically for stainless are cut at a sharper angle. The reality is a good quality jobber drill will be quite happy doing occasional stainless work. You’d only have a separate set if you were in a workshop.
If you buy a set of black Dormer drills they’ll probably be the only drills you’ll ever buy and you’ll wonder why you ever wasted your time with anything ‘branded’ from Screwfix.
Jonny69-
Just to add to the "how to drill" tutorial, ordinary HSS jobbers are fine on the normal stainless grades you'll use at home (304,316) as long as you feed fast enough to avoid work hardening. Really needs a pillar drill, as wandering around with a hand drill inevitably leads to one side rubbing even if the other side is cutting.
gbj_tester
If you’ll entertain a potentially silly question, why not cobalt instead of HSS if used on stainless steel?