Basically Thatcher once said that Owen's natural home was in the Conservatives so with any POD but maintaining David Owen's personality and politics put him in the Conservatives.
Everything I've seen convinces me this is practically impossible. Essentially everything that happened in OTL could not have been better designed to drive Owen to the Conservatives but he still refused even when he had no other option but the political wilderness. Basically it would conflict too much with his political principles. Things might have been a bit different if the Conservatives in that era had a wet leadership but I still say it's a long shot.