I hated lovefilm, too! Amazon was good for awhile, but they purposefully slowed down send-outs (we were with them twice, and you could tell that the second time, after they had started unlimited plans, they were slowing things down). And the fact that Lovefilm is taking over soon made me avoid them for repeat business.
We're with Blockbuster now, very quick turnaround time. If you mail a movie back on Monday, they will receive it and send another out on Tuesday, and you'll get it Wednesday. At least that's how it works for us. They offer a two-week free trial, but I have a Web site link that offers one month free:
http://www.blockbuster.co.uk/BBSiteContent/Affiliate/WinterOffer.aspx. As this is called a "winter offer," I'm not sure if it's still good, but it's worth a shot. Otherwise, if you use cashback sites like quidco.com, you can get several pounds back for signing up if you access Blockbuster through the quidco site when you sign up.