Just fitted my AMBER PERFORMANCE DUMP VALVE, and took a few pictures while I did it to help others if they decide to get themselves one of these. They really are top quality pieces of kit.
Right, First off I disconnected the MAF cable and opened the airbox lid by unclipping the four clips on the corners of it.
Undo all the the hose clips with either a large philips screwdriver, or use a 10mm socket and ratchet.
Pull the MAF up and towards you to remove it from its position, DO NOT damage the honeycombing on the inside - vital to the running of the car.
Remove the hose that goes into the top of the original DV - this has one of those annoying hoseclips on it - i ripped mine apart and gently pulled the hose off.
For ease of access, I removed the pipework that runs down to the DV so that the new one could be attached to the pipe and secured a bit more easily.
Pull the old DV from its RECIRC mounting and dispose of it - mine took a few whacks to loosen off, but it came off eventually. Now push the silver plug inside the hole and retighten the hose clip.
Push the new DV into the pipe and tighten the hose clip, and now reconnect the pipe to the Y-pipe and tighten the hose clip. You can choose to lay the pipework and DV in the original position, or turn the hose round in order to have the DV pointing up near the battery as I did.
Make sure everything is nice and tight, reconnect the small vacuum hose onto the top of the new DV. You can use a small tie-wrap on the hose to hold it in place if desired. Reconnect the MAF harness, making sure the connector isnt stressed.
Close the bonnet, start her up, warm her up and go into town and scare the grannies 
I am not responsible in any way, shape or form for injuries, death, destruction or excess time spent coming on and off boost as a result of following these instructions