Setting the default content font

Hi,
I have a problem with the default fonts for my site storrington.org.uk

The content font in Aegaeus Appearance/Theme Options is set to 16px Helvetica which I believe is approx the same as 12pt. Custom typography is not enabled.

In the default template for pages and posts, the paragraph setting defaults to 12pt Georgia. However, in reality the content appears as approx. 9pt unless I specifically override it (highlight and click 12pt) and it appears as Arial/Helvetica not Georgia (which is good – I don’t want Georgia).

Please can you tell me how to set it so that it really does default to 12pt Arial/Helvetica?

Thanks,
Andy.