URL redirects after moving Wordpress site to new host

I am moving the hosting of my Wordpress site from Fasthosts (fasthosts.co.uk) to Synthesis (websynthesis.com). With Fasthosts, all my URLs have had to contain /index.php/ in the middle of them. I won't have these with Synthesis, so I want somebody to ensure that all the old URLs safely redirect to the new URLs.

Please let me know how you will do this to ensure my search engine rankings don't suffer, and please let me know if it can be set up before I change DNS to Synthesis.

Thanks,
Dan