With thanks to Stephen Newton my Blogger inflicted formatting woes have been partially fixed. IE, at least, now doesn’t show huge whitespace after the first post (on my computer anyway, contact me if it’s still screwed on yours).
Update Blogger are responding to the problem, sort of.
(I promise I’ll go over to WordPress one day. But if I want to port across all of the archives I’ll have to wait until Blogger is sufficiently fixed to be able to update all my archives without crashing………)