O2 announced that its online upgrade offer sold out within hours and also commented on the down time experienced. "We had invested heavily to add a huge amount of additional capacity, 250 times its normal rate, and back-up systems. We tested this carefully in advance. The massive simultaneous crush exceeded even our worst case assumptions. Demand was at 13,000 orders per second. Frankly, we have to admit we just weren't prepared for this unprecedented level of demand. No website is."
Apple is aware of the shortage in the UK...
"We also used the registration data to keep Apple up to date on the phenomenal interest and to support our orders for the phones with them. We have been working continuously with them to get as much stock for the UK as possible. Unfortunately, they have only been able to supply a small proportion of the number of phones we asked for, because they are launching simultaneously in 22 countries. We are confident that over time we will start to get sufficient volume to meet demand, but it is likely that stock will be in very short supply for some weeks to come."
"We will continue to work closely with Apple to get as much stock as possible for the UK. We will also continue to use the principle of first come first served as stock becomes available for both online and in our stores as we feel that is the best way to be fair and equitable to the many tens of thousands of customers desperate to get one"