According to a report from the PCR site, Apple has screwed up and "The UK launch of Apple’s iPad 2 will be delayed..." The report states that the delay to the appointed March 25th delivery is "due to an error in shipping the device to its UK stores."
Apple has denied it.
PCR quotes Robert Peckham, former executive director of the Mac Technology Association reseller group, stating that "a mistake in shipments means that UK Apple Stores will not receive stock in time for the anticipated launch time on Friday morning."
This means the iPad 2, which is not yet available for pre-order in the UK, won't be available until around 5pm on Friday.