Thanks for the replies chaps, a lot of useful information here. Good lord I hope the one politely threatening letter will do the trick. I'll post my progress.

Hello everyone. I'm looking for a bit of advice:
Worked 2 months for a company which I gradually learnt was a fairly unprofessional (albeit legitimate and successful) organisation that sent me confusing briefs and wasted a lot of time. I really went that extra mile to untangle the briefs and tell them what they needed to do.

Delivered the work, some of it had required outsourcing (which I was transparent about).

Over two months on, no payment, endless calls to them, it always appears that the person I need to speak to is unavailable. They've blocked my email provider's IP so I can't email them!! I have the outsourcer rightly giving me grief for his payment.

What do I do? What can I do? I'm currently writing them a letter politely threatening them with a debt collection agency. Is that realistic? Is a small claims court threat more likely?

Any help much appreciated.