Anecdotal, I know, but I was speaking to my girlfriends dad over the weekend.
Self employed builder, has a 4 labourers to help out. They get £7 an hour at the moment, slightly above minimum wage.
Once this goes up to £9, it means he has to be paying £80 more per week per staff member. £360 more per week in total, added with the costs of materials increasing over the past couple of years means this is soon going to be unsustainable. Add in the changes to pensions and you're going to be looking at a hefty sum.
Of course, all these charges are going to be passed on to the customer. They'll have to be paying more money for the same amount of work.