Don't!
Three undergrads just 'successfully' did this. It's believed they did it in yr 2 too, as recruiting others started then.
They got discounts for introducing each other to the service, then rewrote. They've just announced 1st's. It was assumed they'd got away with it because of lecturers glowing praise, despite rumblings.
Those they tried and failed to recruit were left knowing. One threatened at the time to report when they tried to recruit in yr2, got threatened with being reported as part of it, if they did.
Subsequently that student found themselves accused of other serious wrongdoing leaving them busy defending themselves and afraid to rock boats.
They then dropped out very late on, demanding to resit their 3rd year.
They say it's necessary, personal, and the only way of separating from what they got dragged into, but the rumor's they've gone to the Dean, exposed a complex pyramid system and are being allowed to resit as part of it.
Disgust and the unfairness of it has fueled others that knew, and there's been blackmail. (There's a claim they're giving it to the re-sitter) It's destroyed relationships leaving everyone back covering.
Another student, with a 1st earned by their own talent, feels it's now devalued. Another, who feels their 2.1 should have been a 1st, thinks they've been downgraded to avoid too many 1st's.
There's threats of flash mobs at graduation ceremony and even if they buy their way out of that, they've left their future's at risk if they launch a career based on fraudulent degrees.
Short term gains, Long term disaster, they'll be looking over their shoulders a long time. It all stinks.