3 years ago, I was employed Sept - Feb, then signed off sick Feb-May then my employment ended. I also attended a course during that time which was dependent upon my employment so that had to end too.
My employers were awful. I am physically disabled and they made me drive long distances and based me in an office with no suitable access so I had to climb stairs (toilet based on different floor etc).
I got support from CAB who suggested I take them to Tribunal for discrimination. They eventually gave me a small payment (£2K), a plain: '52 worked here from X to Y' reference & I signed to say I'd not discuss it. Ugh. Ditto with the Uni course (no payment obvs).
Much bad feeling.
I am now applying for a College course. I need to document the work I did at old employers / Uni. I can do that. It is possible Collge will contact either employer / Uni. Can they give me a bad reference / cast doubt upon my documentation (I have no doubt they might as they behaved genuinely badly / spitefully, according to CAB employment lawyer as I also unofficially 'whistleblew' about poor practice in both linked places)
This was all in England, circa 2018.