Why stainless?
I find that so long as the screws are of good quality & coated (zinc, japaned, ‘gold’) then they don’t rust unless immersed in salty water! And even better when capped off in coloured caps that seal them in. (Pro-Dec)
Favour Hilti for most of our fixings (hammer-ins, tec-bolts, some self tapping / self drilling screws) and B&Q trade for the rest of the assortment…and any special stuff such as ‘thunderbolts’ ordered online (you’ll probably never use expanding bolts again!!)
Dave