Pros
I worked for IQPC London for two stints which total approx 5.5 years service. The London office is highly successful business run by fantastic event professionals. I was lucky enough to go through the MDP scheme (Management Dev Programme) and can safely say that IQPC assisted significantly with my personal and professional development. I joined the business as a junior Sponsorship rep and left as a divisional sales director. I would certainly consider working for IQPC again (yes for a 3rd time) if it was right at the time. Please don't be put off by any of the negative posts, these are clearly the disgruntled people who didnt make the grade and need someone to blame - other than themselves.
Cons
Dont dispute the fact that you will have to work hard on lead sourcing within a sales role, so be prepared for this. Never bothered me BUT had to be factored in to the way I wanted to work.