1. You should have paid the fee initially, not when you felt like it. It sounds like you are pi55ed off because you didn't get all the uniform/business cards associated - even though you didn't pay for them.
2. that being said, if you have not used the uniforms and not recieved anything else. It's not like you are being unfair not to pay the £200 (IMO) at this stage. They loose nothing.
3. You may screw yourself over for getting a reference (if you want one).
My 2 pence ;)