Freelancing in UK (at least when I did it) was more a matter of knowing the right people in the charter operators i.e the ops managers, chief pilots and ops staff. Having a few relevant, current type ratings also helps.
Once you do get offered some work just do a good job, be flexible and at all costs do not upset the customer. You are then likely to get offered more work and through this you will meet other people who may offer you work.
Upside is the variety, good daily rate of pay and spending time at the kind of places that wealthy people go to.
Downside is that you are the first to go when work dries up, you never want to turn work down for fear you may not be asked again, you are a slave to your mobile phone and customers can be a pain in the a*rse (always late, changing plans at the last minute leaving you to grovel to ATC and apologise to everyone else).
Must admit that I loved it though!