I'd stick with slabs personally.

Hi, I agree with Mg, I don't see any point in the plastic framework, you need something which you can anchor the greenhouse to, slabs or edging stones, then if you want to put gravel down, just cover the ground with a weed suppressing membrane, and lay on that, Derek.

ok thanks got that sorted what about wood vs aluminium some can be bought for virtually the same price in the midrange £1500 bracket

We've got aluminium and are perfectly happy with.