Again, anecdotaly, a friend of mine was working on the roads as a sub connie (CIS) for £9+ an hour 5-6 years ago.
Recently there was a job advertised for a similar position, working on repairing the roads (which is a dangerous job) - £6.78 an hour.
It does seem the minimum wage is turning into the maximum wage for a lot of employers and it does seem hard to argue against that an increase in the supply of workers will depress the wages needed to pay, that's just basic economics.
I think the problem is the other reports that show no effect on wage depression are using national averages and all ranges of jobs, which is valid thing to do, but in localised areas and sections of work there has been a dramatic effect. And for those that has affected, they don't care about national averages.