Around 35,000 delegates are expected to attend.
Rob Harrison, Chief Operating Officer at Congrex, said: "We have been in discussions with the ESC on and off for a couple of years to make them aware of how we can help them.
"The key to securing this type of business is making sure that the allotment of hotels is in place and that there are acceptable rates for the profile of delegates coming in. Making sure that this was in place in advance of any announcement is one of the key things we have been working on over the last few weeks.
"We are expecting about 40 to 50 per cent of delegates to book through the official housing bureau, particularly as there is a lot of availability in london. We are expecting 12,000 to 14,000 delegate to book through us.
"For Congrex, associations like the ESC knowing that we can assist them in this way on an individual service is very important because there are lot of associations out there that think PCOs only are to be contracted for a full service. Being able to offer an individual service like this and a link in with the city by having a number of partnerships in place can benefit associations immensely."