The best kind of hosting for SEO is a server based in the county you are hoping to target for visitors.
If you want to rank well in Google.co.uk or yahoo.co.uk, you will need UK based hosting.
Not just any old hosting, reliable and depending hosting that is up 99% of time, if googlebot and yahooslurp do visit your site and your down, it will count against you.
You will also want to make sure you have no banned or blacklisted sites on the same server as you.