Firsttunnels do fruit cages. They are easily assembled and sturdy. I have actually moved mine on one occasion with no problems. Downsides are that their side netting is too thin - I startled a pigeon that was outside when I was walking to the cage, and it simply flew straight through the plastic netting tearing a massive hole. Secondly, it will take a lot of fruit to off-set the cost of the cage.
Removing the roof netting is a real hassle. The last two years we haven't bothered as it takes so long and you end up with holes in it. We just risked not having too much snow, and accepted if it needed replacing then so be it.
If I was doing it again, I would probably only put cherry trees in the fruit cage, and any soft fruit like raspberries into a polytunnel.