How else do you judge the merit of a policy except by looking to the effect it brings?
By looking at
the effects it brings. And by looking at the effects of the alternatives.
Its obviously more 'efficient' for a company to employ less workers, but that is obviously terrible for society.
In the short term, yes. In the medium term it depends on whether the people have the skills to find different jobs: I'm not going to argue that unemployment benefits anyone. In the long term it's likely to be a good thing. We would be much worse off if we still had 80% of the population employed full time in feeding us because we wouldn't have as many people free to write books, discover new medicines, look after old people, etc.
I forgot to say that poverty in the UK has been rising significantly.
UK poverty measures seem to be more a measure of inequality than absolute living standards. Obviously this is still worrying though.
Corporations and the super rich get away without paying tax
Corporations can't pay tax as such. The effects of any tax on corporations will be borne by some combination of owners, staff and consumers. For example VAT is paid by companies but mainly falls on the consumer in the form of higher prices. You could argue that corporation tax should mainly fall on the shareholders, so I suppose we come back to your rich people point. In general the rich pay a lot of tax, though I could understand if you took the view that they should be paying more in proportion to their income.
Only the state can be blamed for its conscious decision to roll back social support and spending (not to mention taxes)
I agree. Get rid of all zero-ratings and exemptions for VAT and use the revenue to increase benefits (especially for those working on low incomes -- you can make work pay in ways other than punishing the unemployed). Reduce subsidies to businesses and reconsider "pro-business" policies in general.
now corporations outsource production to countries with cheap labour. None of that employment goes back into UK society. Does it benefit the countries where the cheap labour is either? No.
I disagree. People in the UK get cheap stuff and the jobs go to where they are needed most.