Good on you James.
I've just received a £40 payment from a customer that has owed it since October last year. Despite numerous texts/calls promising she would pay, she never did.
Anyway, sent her a "Letter Before Action" letter from Thomas Higgins and hey presto, 5 days later, she pays.
It used to bother me that she thought she could get away with it, so I went the Thomas Higgins route

Only ever had it done to me twice before, one of them moved out of the area, so I wrote that off (£15). The other one lost his job and was skint, but I saw him in the pub one night and he paid up (£18)

£8 or £80 it would still wind me up