I've always said that I think KC would take Harry back, but PW never will. The stuff he said in Spare was just too cruel. God knows how bad it was behind closed doors. So Harry may be able to come back to Britain while KC is in charge, but when PW is in charge he'll give Harry the same treatment KC gave Andrew. Harry will also be booed wherever he goes in Britain so he will probably have to live on the downlow.
I think ultimately Harry is very stupid, so he is easily moulded into the image of the person closest to him. That means he was being productive while under the influence of PW, but under the influence of ILBW, he became conceited and hysterical. The drugs will have deteriorated his mental functioning as well, which may mean he can now never be deprogrammed, even if he were back in the bosom of the royal family. It's a great shame that he ruined his life to duck a pretty-ish not very talented actress for a couple of years.