Like Ellen K, I have just bought one of the so called Pro range of tunnels from feelgood, with the same view that once the cover goes I'll replace with some 'proper' polytunnel plastic. I also plan on making the frame as robust as possible when I set it up in the next couple of weeks, i.e. extra bracing and some stout posts to anchor it to.
Those buyitnow prices on eBay seem like a good deal.