The law of unintended consequences, as always.
More staff will be let go, and the rest will have to work even harder to keep costs down, especially in small businesses which cannot keep absorbing the cost. Fewer staff will be hired in the first place.
Prices will rise everywhere due to larger overheads at every stage in the chain. Inflation will increase. It will be interesting to see what the BOE make of this when they announce their next decision on interest rates.
And my personal bugbear: most people's wages above NMW will not have gone up by as much, therefore, once again, narrowing the gap between new and experienced workers, and those who have invested time and money into gaining qualifications. Of course, if you are a top earner that will not bother you too much, but those on the lower rungs will soon be among the ever-growing percentage of people who earn NMW in the first place.