Don't bother with a Workmate they are useless.
A good vice fitted to a solid bench is much better. Have a look at Paul Seller's bench making videos for a very traditional design which happens to be the best and simplest.
Or skip benches altogether and go for Robin Wood's "Bowl mate" (scroll down)
You hold things in the space with a wedge or two, or rest them on the end notch whilst you hold with one hand and chop with the other. All sorts of variations are possible
Speaking (well...typing...) from bitter experience, a Workmate is OK as a sawhorse, but no good at all for planing - it's the wrong height, and nowhere near heavy and rigid enough. Nothing beats a good heavy bench, in the end; especially one that is just the right working height for what you're doing.