I don't think Tories+Nutjobs' second preferences will have a natural majority. The natural British majority is Lib-Lab. If AV was going to work in the Tories favour they'd be all for it. It's a difficult, technical subject to predict with any certainty but if they're against it it's a strong indication it's a good thing.
Incidentally, this isn't a full-on Tory government IMO. One of those is worse than this.