Just got this email from buymobiles:
Thanks for your order. You have passed our initial security check and your order is ready for processing however your Sony Xperia S is not in stock at the moment.
We expect it to be available again within 10-15 working days, so we are going to temporarily hold-off from processing your credit check until it is back in stock.
As soon as it arrives we will process your order, send you an email, and ship your phone for next-day delivery.
Kind regards
Customer Services
0844 880 8100
Mon - Fri: 8:00am till 5:30pm
Sat: 9:00am till 1:00pm
Crap, I'd called them today too at 5.20pm and up to then all was still go.