Daz, it's best to keep on top of it, regular collecting - rarely (if ever) owing more than 1 clean and giving them plenty of options to pay - cash, cheque, online banking or paypal.
for some of the out of the way custy's who are 'out' when i call we leave a letter letting them know i called and sorry
to have missed them follwed by monies due and ways to pay - then i add a hand written note asking for payment within 3 working days...
99 out of 100 payment arrives within 2 days.
new customers are politely reminded that it is payment on completion/ that day if paying online and this seems to
keep most on the straight and narrow.
firm and polite works well - otherwise it all just slides and the debt list is huge before you know it.
Darran