Far further left than you think. He is neither Tory nor socialist. He is a populist. Which means he is first about Boris and next about ordinary people. He is from the establishment in wealth and education, but far too maverick to be part of it in the embedded sense. His entire Downing Street machine is anti-establishment. And if he wins it will be because very large numbers of working class people, who deserted from Labour in the New Labour Blair days, will have voted for him. Not for the Tories, but for him. Because of Brexit, but also because they believe that Brexit will improve their lives and resolve all that has gone wrong for them.
And because of that they will have very grand expectations, which cannot be met by any more austerity, nor timid spending plans. His new northern voter base will have priorities which are real, deserving and urgent. Boris will have to step up to the plate. So if there is a Tory majority next Friday morning, you can expect the most left wing government of that party, since the days of Harold Macmillan. Socially conservative maybe, but economically Keynesian, with a lot of spending and loads of borrowing. Austerity looks to be over whichever way this election goes. Thatcherism is already dead.
This assumes that those northern Labour heartlands swing behind the Conservatives rather than frittering votes on the defunct Farage. If they don’t and on the day stick with Labour, Boris will have to hold all the Remain seats of the south to keep his job. That might be a good deal easier said than done.