I have been using tech results for over 10 years now, they are always reliable with their service offering, even when i am not in London office they still manage to get my work done without any issues.
Their call center is also very efficient and helpful. The only thing i dislike about them is sometimes it can be hard to find someone who deals specifically with your issue within the team but tech result's customer support will help you out. We use their hosted desktop solution which has helped us reduce our cost significantly since we don't need an expensive dedicated server anymore.