I use a fair number of S&W hoods and step rings: they come in pretty much all shapes and sizes: as a sort of generic brand, they may not always be sold by name on Ebay, but I can name one dealer who has a lot of them. I think they're quite sufficient for a lot of things, (round hard plastic is usually my preference, with metal a close second) and hold up just as well as you may need, to my experience.
What I use with my Mamiya is just one of the big non-foldey rubber Mamiya ones: since it works with both of the lenses I have for it, I actually swap it between them when I change lenses, (cause it's beeeg: also, in my case, the hood wears a step-down ring to the filter size I use, so this keeps it all fairly small. (the Mamiya rides lens-up in a bag, so the hood's size isn't a big issue) You could possibly replicate my scheme with one of those Hama-style three-position hoods, which seem to be nice enough, and conveniently-threaded. )
There's a specific Ebay seller I have gotten a lot of that S&W stuff from, I forget if it's OK to mention someone in particular. But most of his stuff is nice as well as reasonably-priced. The nice thing is he usually has all that stuff in whatever depth and size you may need.
(Oh, and on this: )
"Now is the 70° angle for 35mm format (24x36mm film frame) lenses - and would that specification be different for a medium format wide-angle lenses?"
Nope, angle of view is angle of view. By format and focal length, these will change relatively-speaking, but as long as you know the angle of view of the lens and film size you want to put it on, 70 degrees is seventy degrees.