Corporate and VOIP use
UK telephone numbers beginning '05' fall into three categories:
A few old-style freephone numbers starting with 0500 are still in operation, but will be withdrawn during 2017. Newer freephone numbers begin with 080.
055 corporate numbering
These numbers are intended for large organisations who require their own large blocks of dedicated telephone numbers that are not associated with a specific locality.
056 VOIP and similar
Officially designated for 'location independent electronic communication services', 056 numbers are mostly used for VOIP phone services. Such services have also been able to use standard '01' and '02' area codes since late 2004.
Numbers beginning 05600, 05601, 05602 and 05603 are currently in use.
05xxx xxxxxx is typical for most numbers, with 0500 xxxxxx used for the remaining freephone services in this range.