Try the late payments act 1999 revised 2002 they will soon cough up then mate if you cannot run don't do the chasing let someone else chase with counter charges for late payments do it for you,there is a true saying in business no mates rates and be very hard nosed but you must stipulate this on your quotes and invoices and your best having it in small print at the end of your terms and conditions no one ever reads the small print hope this helps you in the near future,for all information just google up late payments act 1999 revised 2002 and you can download all the information