The money is not the issue. I am well paid for my work and am grateful that I am where I am. Working up the front end of brand new technology has me like a kid in a candy store.
The point you make about the agency loving me however is difficult - on the one hand you suggest to be (and correct me if I am wrong here) straight down the line with these guys and say contract says X, give me X. But if the company I supply to says no - on the spectrum of options are: scream ever louder and risk your professional reputation, quietly insist they owe you and I am expecting them to pay, or be a simp and tell yourself better luck next time.
The clear option in these I think is the middle one. Yes they are unlikely to pay, and added to that is the small issue that the end customer doesn’t have a clear PoC with regard to these issues. HR - speak to finance. Finance - speak to HR. And around it goes.
Sorry but I worked in an agency, was a manager in an agency and part owned an agency over 27 years - all IT in the Thames Valley. I also took the industry exams (bet you didnt even know they existed) and when it existed sat on the local branch of the industry body.
With regard to right:
Either you are a PAYE temp or you are a ltd co contractor (of which umbrella is a subset).
If you are the former then you have various statutory protections - one of which is the illegality of a pay when paid clause. That is because Temps are deemed to be the wrong side of the power dynamic in the employment relationship and thus need protecting.
If you are the latter then you are not a person you are a person working for a ltd company - that ltd company has a contract with another company (usually the agency) the contents of that contract are king. As a company you do not have the protections of an individual as companies are deemed to have sufficient expertise to be able to negotiate and sign contracts understanding the risks and rewards. Unless you are one of the minority who have a direct contract with the client (usually when extra control of IP is needed) then your B2B contract with Agency Ltd is the only thing that matters along with all the particulars of assignment etc. If you decided to opt out of the AWD that is your companies decision.
I will ask again as you ignored it
What documents were you given prior to commencing the work - what were they titled, what notice was written into them ?
A lot of what you wrote at the beginning was written as if you were employed as a member of staff, you are asking about statutory rights and protections that you think you might be owed AS IF A MEMBER OF STAFF yet you say you have contracted for years.
If you are a working through a LTD the rights you have are yours as an individual against youcangetjules LTD as that is your employer.
Client limited has NO legal employment responsibilities to you (other than some H&S) unless you want to argue that you were in fact a disguised employee (which you may very well be from the working conditions you describe)
There is no way to ascribe employer status to that company and demand/claim any type of recompense without getting the agency involved and questioning their legality/compliance with laws as well.
Some of the biggest are the sharpest with their practices
So make a decision and stick with it
Be a ltd co contractor, get you big boy pants on, accept you are swimming with sharks and take the hits along with the higher £ph and reduced stoppages
or
Decide you want protections, work under PAYE rules, accept stoppages and the extra security.
There is no halfway house that exists other than in the minds of many contractors who are only that on paper.
Monday morning rant over