"Gross value added (GVA)" is a measure of the value of goods and services produced in an area, industry or sector of an economy - so, for example, England in comparison to Northern Ireland attains around £5810.00 more value per person than the latter. Given this however GVA is not necessarily income per person, that would be median household income which can be seen in this PDF for example (
http://www.ons.gov.uk/ons/dcp171776_341133.pdf). Of course, given that median household income accounts from the United Kingdom as a whole it will also include the wages from London which should indeed inflate it.
Labour productivity is the amount of products and services made per person, so whilst you could say it is the number of hours worked, you must also take into account the goods created and the capital used to produce such. As for Scotland, the unemployment rate takes into account only the working age population, so whilst 8.3% of the UK population is from Scotland, there will be significantly less of working age most of whom will be employed, hence the low employment.
Expenditure on public services is exactly that - the budget spent by the government on the public sector including education, health-care, police force etc. The gap should not make much of a difference given that living costs in Northern Ireland for example are significantly lower than in England, so nurses, police, teachers and so on will require less pay. GDHI does not just take into account tax, it also includes the costs of basic essentials and house prices as well as factoring in those on benefits so you could say that it includes the unemployed. Furthermore, the disposable income stated before makes the English slightly richer as it takes income into account after said taxes and essentials though it hardly makes a difference.
Finally, the statistics for Northern Ireland and Wales aren't as impressive due to the history of those places. In the case of Northern Ireland, this was due to the combination of a lack of investment in the area (due to the Troubles, respectively) and increasing competition from other areas of the United Kingdom alongside other countries which caused industries such as shipbuilding to decline rapidly.