Don't forget, that until you get paid you have worked for nothing.
It might be looked at by some as money in the bank but it certainly ain't in your bank, it's in someone elses.
I never have bills outstanding at your amount as i'm a window cleaner but it is disheartening to work for 3 months without getting paid.
The bottom line is do you want to take the chance of getting no more work from them. No-one else can make that decision for you.
But as long as you go about it in a professional way, no-one can have any cause for complaint unless they are going to try it on again in future and in that case you are well shot, whether you realise it at first or not.