I only have about 10 posts, so that shouldn't be an issue.
I have narrowed the problem down however, it only seems to happen when the results are in vertical mode. When the results are set to horizontal, it works absolutely perfectly.
So just to recap, when the results are set to vertical, the search form doesn't return anything for about 10 seconds after the page has loaded.
FYI, the search form I am using is on the following site – http://www.pilotprize.co.uk/uk-charts/
There are two searches on there, both identical, but the top one is vertical, and the bottom is horizontal.