Thanks for your reply. Here's what I did:
I. Optimized all PNG's & the header image
II. Added gzip to my .htacess file (from GT Metric, which was 2s faster that the Apex code!):
III. Added the W3 Total Cache, but disabled it for now on your guides advice.
I have the load time down to 7.3s, which is a great improvement from 16s, but it is still rated E, and a way off the 3 seconds recommended time. I'll attach the report from gtmetrix privately.
Is there anything else that could be holding us back? I've used a lot of buttons on the site - all the flag/country icons are individual buttons (and this menu has an iPad version with 4 columns instead of 6, the only way I could get it to be responsive, so there is a second hidden menu), all the media icons are buttons (SVGS) so I guess we are a little image heavy.
If i can't get the load time down then I may have to seriously think about whether pro is the best solution, but I have put so much work into this already!