Here's the thing, Labour have never been "Tory lite", that's just something the far left voters say because they disliked the party becoming left of centre. They are still a left wing party, a left wing party is not a lite version of a right wing party. In the modern world you cannot win a UK election by being far left or far right as you will never get enough voters to defeat a centre left or right party.
Losing the party's far left stance with Corbyn is a start on the road to electability, however convincing the far left voters that left of centre is not the right wing is an almost bigger problem.