I know OPKs work really well for me, but as I said I don't have PCOS.
Just remember to take the OPK in the afternoon and to have held off from going to the loo for a while to increase concentration. I hold on from about 3.30 until I get home and test about 5.15pm, takes practice but I always get results so I stick to it. I usually get a light line, and then the positive heading into O, but I have had +'s for a couple of days at the same strength which can be a bit confusing.

Hopefully someone with PCOS can help you here.