Number of working age households found in:
Northern Ireland benefit cap impact assessment: http://www.dsdni.gov.uk/impact-of-benefit-cap.pdf
Total number of people affected worked out as 3,120 children (mentioned in IA) + 37% of 620 HHs are couples so ((0.37*620)*2) = 63% lone parents (0.63*620) = 3,969.
Northern Ireland UC impact assessment: http://www.dsdni.gov.uk/uc-impact-booklet-transitional-protection.pdf
DSD statistics on SRS HB claimants: http://www.dsdni.gov.uk/index/stats_and_research/benefit_publications.htm
GB numbers from Stat Xplore
Personal Independence Payment
Benefit statistics for NI: http://www.dsdni.gov.uk/index/stats_and_research/benefit_publications.htm