OK, now I know why I wasn't experiencing the problem and others were...
Our old ad provider obviously switched themselves off today, the ones who went bust that is, because it was the ad code that was causing the delay, while it tried to connect to the ad server to get an ad. I didn't experience it because I'm a Premium User and so I didn't see any ads :-)
Its now, finally, fixed and some extra tweaks to the PHP engine should help too (like I removed the Java support since we don't need it any more!)
Sorry for the aggro.
Now, tell me how we should go about the COPPA issue and kids using the site...
Steve.