In reply to n-stacey:
What are you going to use them for? I just bought the £130 Tacx (cheapest) ones because I'm only using them for gentle warm-up and warm-downs at the track. They are fine for that though would be a pain if I needed to collapse them to transport them as that requires an Allen key. If you are hoping to train on them then a turbo would be better. Sure, you can get ones with resistance but for big efforts you really do want to be sure you are not going to end up flying through the patio doors. Hinged aluminium ones are best but are pricey.