From what I've read... the full on JCW will be a seperate car (with 4 wheel drive ??) and will not be an upgrade bolted on at the dealers. I suspect a handling upgrade will come out to compliment this stage 1 tuning kit...
I would be tempted if I had £1k sitting around, though would rather spend money getting the GTT stealth cat done first, probably followed by some strut braces once they are released by GTT.