I know that outside Europe one often needs overflight permits, but I know of at least four overflight agents and that is just in the UK, so this seems to be a well sorted business.
Do people use Jepp primarily as a one-stop service?
ISTM that within Europe there isn't much to do because (at this level of ops) you deal with handling agents anyway and a phone call to one of those will sort things for you, and presumably that is all that Jepp are going to be doing anyway.