I replace 16G last Friday and they sent it to me via UPS no problem. Took the whole of 36 hours from request to receiving it. Problem with proximity sensor and new one had same problem.
Just got a call from Apple again saying they need to replace the replacement as it still has the sam

e problem. They gave me 48hrs to receive the replacement via UPS.
So seems they have replacements in stock. They suggested I picked it up from one of their stores (Southampton or Kingston) but I requested they send it to me as I do not want to drive 60+ miles to pick it up.