Single source certainly isnt going to help your case.

TBH alex from what i know of your current job, its blatantly employment whatever way you look at it.

In order to get outside of IR35, i insisted on the following conditions:

I could send another employee of my company instead of me if they were suffiecently experienced (highly unlikely id ever have such an employee of course as there were only a few people in the country at the time with similar experience, but the clause was still there)

I worked whatever hours i wanted, they had no say over when i worked

I had the choice with each project if I accepted it or not, they didnt have cart blanche to assign me work

I was allowed to work wherever i wanted, so at their office, at my office or anywhere else i saw fit, in fact i exercised that contract a few times including doing chargeable work while i was on holiday in america

I had to provide certain equipment needed in my role, thus requiring an investment that would not be expected of a "normal employee"