Changing Domain Extension

I've got a site at the moment on a .co.uk extension that i'm planning on doing a lot of SEO work on. But i'm thinking it might be best to switch to a .com extension to get the most out of the SEO work i'm going to be doing.

But, the .com extension of my domain is going for $300, is it worth buying? Or should i stick with my .co.uk?

Thanks

if your website is for Uk people stay with Uk. But the domain extensions doesnt make difference for google mommy because she loves them all