Hatemyjob, i wouldn't hassle too much, they are busy people also i believe even after the OPQ it says the results will be back with you in 15 working days.
I took Stage 2 on 1st May, several people have their results from this day and the 18th and 19th May, i haven't.
I do share your concerns about HR, my 15 working days has passed and wa told today they will get back to me in 2 working days !!!. Unsure what this means, have they lost it ??? or still laughing at how many i failed ??? Either way i dont want to hassle them as im sure it wont help.
Good luck with your OPQ results, i know others on here have waited more than 2 weeks or so to get results from it.