What is going on with adsense? I used to make good money displaying other peoples ads on my sites. Now one of them has just broke into the top 10 of Google.co.uk with one of the most competative keywords and with over 2700 unique hits, I am getting 3 clicks and $0.19 on average! This is a joke, why should I be advertising, taking up space etc on my own high performing site just for 19 cents a day?

This may sound harsh but, it might not be Google's fault, but your fault....

Have you tried adjusting your ad placement? Have you tried different ad formats? Have you tried different ways of blending the ads into your site? Have you tried adjusting some of the keywords on your site?

why should I be advertising, taking up space etc on my own high performing site just for 19 cents a day?

Then don't!
It's as simple as that.