I had a top made with no corner windows, like the RV8.
I just unclip the two main snaps and throw it back. When it starts to rain I just reach behind me, pull if forward and clip the two snaps. Takes no more than 10 seconds either way. I don't bother with the 4 tab snaps, they don't seem to make a difference. I've even managed to put it up while crossing the west gate bridge (where you can't stop) in peak hour traffic at about 30MPH. The folding frame is the one that came with the car, a 1975. They will fit on earlier cars.
It's the corner windows that are the problem. It makes it hard to get the roof down and if you crease them they last about a month. No modern convertable has those corner windows, so neither do I! I don't miss them at all. Infact I prefer the look without them.
Prestige (amoungst others) do a very nice roof. Just ask for a RV8 style top for an MGB in the material of your choice. No need to get the super expensive insulated/lined top.
I'd advise getting the zip down/out rear window though. Really nice on baking hot summer days. You get the cool breeze without the sun.