It's in and working.
3dfury.co.uk were spot on. Ordered at 11am and it was there for 9am the next day. The £60 without screen was a one off, he happened to have one with an intermittent fault with the screen, which he gave me anyway. I didn't bother trying it, it's just not needed. It's also nowhere near as nice looking as the xk3y site images either, cheapo plastic.
Plenty of room in the xbox (fat), physical install was very easy.
The PDF guide is good. The process varies a little by drive. For my liteon it was a case of saving the key into an original firmware with JF and dropping it on the included micro sd card. This part cost me hours. I was using an mp3 player as a card reader, it kept creating a music folder everytime I put the card in, once I borrowed a phone to use it worked straight off (my phone usb port is knackered). Took me a long time to realise. Future updates can be done from a usb stick, no need to open it up again.
So now I've got a powered Iomega 500GB drive plugged in the back. Everything I've tried has run so far, Black Ops 2, Dishonored, NFS Most Wanted. I can't say I'm seeing any speed difference, perhaps it wouldn't be good with MS if they let it read faster. It is a little off putting at first though when a game is loading, without the thing sounding like it is going to take off you don't know what it is doing. It's a good thing, it's just weird. No more spinning up for loading. I was considering taking the drive out altogether, but I don't think I can be bothered. Especially after the 4 hours I've just spent wrestling with a mates hitachi 59 drive. Enough opening xboxes for now.
I can't say a bad thing about it, well pleased.