non payment of commision

Hi There.

I ran my own renewable energy company for about 15 years and know the lgals about self emplyed but this guy is just a fake as far as im concerned, never pin him down to a straight answer and kept changing his mind on how and when commision was due.

I was ill for a few years and only recently got back on the road as a sales rep. Started work for a wall coating company as self-employed, asked the director on several occasions for an agents agreement but always the same answer "ye ill sort it”. And the pay structure of when i get paid changed occasionally.

I have now left and he is trying to B/S me in paying less than I’m due,(not the way to do things as far as I’m concerned)
I was told payment on £5 per sqr mter plus 50% of any overs, paid on start of job, having had my own company for many years i have always made sure there’s no mis-understandings, "so this is after survey"? i asked "yes" was the answer.
Now he’s telling me that it’s on what I put on the contracts, which will inevitably different to the survey.
So where’s my overs going!
On Thursday i was e-mailed with a statement on what I’ve been paid plus the balance due, i disputed that amount and was told he would look at my queries and get back in touch on Friday.
Guess what he never, just paid the amount he calculated into the bank.
I have pointed out that he should give pay statement on a self-billing system if I’m not told when the installations are going in as i won’t be able to invoice him.
He said "my god you are a stickler for legal’s and detail aren’t you" dam right i am.
I had already told him that if i don’t get paid the correct amount it will end up in court or debt collectors.
He is refusing to send me copies of the surveys to confirm what I should have been paid
I have spoken to a couple of X reps and my interpretation of how the pay should be worked out is correct. Down side is I don’t have agents agreement, but neither does he..

Right that’s the brief scenario.
My question is: If i have to instruct independent building surveyors to confirm correct measurements so I can work out my commission and shows his calculation is incorrect, would the cost for said surveyors fall on his toes and added to the total due?

Regards
Phil