I was imagining to have the whole bed active and if I need a smaller area just cover the un-used part with a sheet of plastic. So no need for a manifold?

Reserve tank is a vacuum chamber right? What is a manifold switch, do you mean I need a pressure switch to activate and de-active the pump to (try) and maintain a constant vacuum level?

At the moment I'm planning to build a table like that in the video, and seal it and use a normal vacuum cleaner. If that doesn't seem to hold strong enough I will try a vacuum pump and hope that has enough flow-rate. I'd quite like a vacuum bag press anyway so the pump could be quite useful.

On a side note, why are the bags for vacuum bag presses so expensive? I saw them around £70 each! Any tips where to get at a better price. Those ones for putting clothes in the loft etc are much cheaper, lol.