Wouldn't be anything like that. FPTP distorts the numbers of seats but not to that extent. Even Tony Blair in the 1997 landslide only got 63% of the seats - and that was with Labour being 13% ahead of the Tories in the vote share AND benefitting from a set of boundaries that was biased more in Labour's favour that the Tories.
Based on recent results, I would say that Con 35% Lab 30% in vote share would be most likely to lead to a hung Parliament with the Conservatives having something like 45-48% of the seats in the Commons. Obviously still unfair though.
(
By the way your hypothetical vote share numbers add up to 110%, but that doesn't change the reasoning 
)