I was looking into this some months back.
I tried a set of Oxford bone dry pants, they were useless, leaks on the second use, took them back for a refund.
Did some research on UK forums bout Oxford, seems they are good at keep you warm in winter but little more.
One buddy at work bought a perfecto suit, he's used it in light showers since the start of summer with no hassles till today.
Now he's walking round the workshops looking like he has a bladder problem.
Builders sell suits for R99, the jackets work well but the leggings start to leak after second or third use. I think the problem is they are intended to we worns and walked in. sitting of the bike rubs the thin rubber lining off then the wet ass steps in.
I would love to know where proper sea angling oil skins are available in Joburg.
A few places sell imitation oilskins, they are yellow with a plastic film over some sort of weak fabric, they soon develop cracks and leak.
BMW sell a rubber lined rainsuite for poss R1500

They sell the leggings separate for about R800, I looked at them and to be honest they didn't look any better than a R250 rainsuit from fool Frottle.
I think waders or proper oilskin leggings are the way to go.
MalcolmT