Where do I control the font of search results?

Not quite sure what you are asking but the font of search results would be the font of posts.

Hi

My site:
www.tinbats.co.uk

Search box on right margin

Enter a search term in post code - try "L37"
Hit Search

Headings from posts appear a grey color
Aschool
Bschool
etc;
- how do I change this?

That is in the Style Posts & Pages section of the theme options. There is a boxes there for the Headline both for when they are or aren't links.

Thanks for that - but i must've done something else that's conflicting

I have in both link and post the following:
padding: 0;
margin: 0;
font-size: 125%;
font-weight: normal;
color: #270691;

The Headline shows different on the results page (where it is a link) than the actual post page.

What happens if you use px or em instead of %
Also are you putting the CSS in HEADLINE Box: Text and HEADLINE Box: Links