Both O2 and Carphone Warehouse are showing no stock of either model of iPhone this morning.
The news comes less than a month after O2 discontinued the 8GB model of the iPhone opting to only sell the 16GB.
The Apple UK online store continues to sell both the 8GB and 16GB iPhone with shipping times quoted as 24 hours.
[Update] The 16GB iPhone is now back in stock on the O2 online store and O2 has reported that retail stores have reasonable stock.