UK Hosting Suggestions (25 - 30 Sites)

Hi,

I'm looking for some suggestions for UK based hosting solutions. I currently use a reseller host with 34sp in Manchester who have been great for years but I want to shop about as I'd like to have the ability to add Varnish Cache and some additional header control for Gzip etc. I'm using perch for building small business sites but they are responsive and want to make sure the performance on the server is there.

Server needs to be able to handle PHP/MySQL (I have a few other CMS solutions to host), PHP 5.3 and ideally SSH access.

Any recommendations welcome