Anybody any experience of either and preferably a direct comparison?

the lockblocks work well – the Fenix flashlight mount is IMHO a heap of poo – I was loaned one to test when they first came out – needless to say I still use a lockblock

I've got both – they are both ok. The Fenix one rattles around a bit more (there's a small amount of play between the two halves), but the twofish one can slip around on the bars. You can adjust the angle on the Fenix one.

I've got a fenix one I could sell you actually – £5?

Thanks for the offer grumm. I've committed to two Lockblocks and just waiting for delivery-wondering whether I did the right thing-sounds like I did!