No, you are not too late at all, at all.
I didn't plant my spuds until May 28th and a second batch on June 5th last year and they all came through with no problems
i've not been to the garden centre for a few weeks now - which seems surprising - but i'm sure there will still be tatties in there.
alternatively, pop into the supermarket, buy a bag of spuds, sit them on a sunny window shelf for a week or 2 and plant them