Churchill: centre-right (but Tory left)
Attlee: left (but Labour right)
Eden: centre-right (Tory centre)
Gaitskell: centre-left (but Labour right)
Wilson: centre-left; Labour right
Home: God knows. Just very very posh.
Heath: centre-right; Tory leftish... drifting rightwards towards the end
Thatcher: right; Tory right (but her Cabinet started out Tory left)
Foot: left (Labour left)
Kinnock: centre-left (originally Labour left - but Labour right from shortly after becoming leader)
Major: centre-right (Tory centre-left)
Smith: centre-left (Labour centre-right)
Hague: right (Tory right)
IDS: further right (Tory right)
Howard: hard right (Tory centre)
Cameron: centre-right, but right from becoming PM onwards (Tory leftish)
Miliband: slightly more centre-left (Labour centre-ish)
Corbyn: left (Labour left)
May: hard right (Tory centre)
Johnson: right (seen by public as centre-right; Tory centre)