Thanks for all the input and help, it really helps to get other opinions and suggestions on the matter.
As it stands, I've spoken to them about it and it looks like this may be resolved without the need for further action, but I will update when I know it's finished.
The worst part is, I worked hard for them, started early, finished late when needed, drove long distances and rarely got money for fuel (average 250 miles a month), alot of parking costs out my pocket, etc etc for not great money. The problems they have come up with, all took place around 3 months ago and it's only last week they chose to make a problem with them. They knew all about them at the time and were happy to carry on, and one was a job I had to correct a mistake someone else made!
Anyway, time will tell.
Sailor48, you describe the way I worked for them, labour only, basically like employed, but self employed.