Our tour guide that never told us his name, was not the best. He would neglect to inform us what time and where we had to meet unless we asked him, but then he wouldn't tell everyone else. If you want a purely Harry Potter experience like we did, dont expect that with the Oxford part. The guide also did not know very much about Harry Potter. Although Oxford was nice, it wasnt as Harry potter filled experience as we expected. But the Warner Bros experience was great. We had both done it before but it had changed slightly which was exciting!
Overall, I would suggest perhaps only doing the Harry Potter studios, especially if you have children as I imagine they will get bored.