Hi James,
Don't worry about the cost of going to court too much (as long as you are sure you are in the right) From what I can gather about the value of your claim, it will cost you somewhere in the region of £100. (which you get back when you win)
Go to:
https://www.moneyclaim.gov.uk/csmco2/index.jspA recent post I made in RE: Getting Paid:
I was owed £720 from one contractor since last May.
Put my claim in online in October (cost £80)
3 days later got call saying "there was no need to do that!"
Recieved cheque about a week after that (including £80 costs)
Withdrew claim - quick and simple!
Still cleaning for them - but payments always on time now!
Another contractor was 2 months late in paying £1,630 owed.
Simply called them to let them know I had filed the claim online and would submit it in 7 days. Cheque within the 7 days!
Awesome!