The North West of England has been taking claims for Universal Credit for longer than any other area. This region alone has over half the total current claims for UC and virtually all the Universal Credit claims from families. (Families includes lone parent households)
By contrast the North East of England has the fewest claims for Universal Credit. The following percentages are extracted from the DWP Stat-Xplore. (A word of warning if you intend to use this yourself, it is MUCH easier to register at the outset than to get logged in as Guest and subsequently change your mind)
Nearly 10% of Universal Credit claims are in Scotland.
As the Department of Work and Pensions [DWP] explains here it is only JobCentres which were already on the list by the end of 2014 which will now take Universal Credit claims from families (Screenshot below, click on image to view in new tab larger size)
The dividing line can be seen in this partial screenshot from Table 4.1
I’m using this interactive map
Workington is immediately BEFORE the cut-off point and therefore is taking claims from families
Clevedon is immediately AFTER the cut-off point and therefore is only taking claims from single people.
This page has more details about the JobCentres where Universal Credit has yet to arrive. You can check your postcode against the index of relevant districts.
I wrote here about lone parents on Income Support moving into the scope of Universal Credit once their youngest child reaches 5.
This tabulation tool from the Department of Work and Pensions shows how many lone parents on Income Support with children under 5 are in each area.
This pdf provides a useful short introduction to the current state of play with Universal Credit (September 2015)
This link has more interactive maps