IoT Hackathon event

I am looking for good hardware (IoT) hackers to participate in a paid for event happening in next spring or summer.
Currently it is early days and I would like to know what the day rate would be for a 9 to 5 event 3 to 5 days in London Travel and hotel costs would be paid if needed. Also, a venue for about 16 people. If any of you have experience with this and pricing it would be really useful.

The theme of the event is large crowd dynamics and/or control. “Large” is 4 million.