£5 for a referral is an "own goal"
This is one of the lowest referral bonuses for any of these sites. If they get flagged for bot use or AI input, your account can (will?) be flagged and investigated as well, losing access to the platform temporarily and perhaps permanently. As well, every person added IS a draw-down on your potential earnings, because gig work is unfortunately fundamentally competitive income even if we should generally assist each other in gig worker solidarity overall. There's no world where £5 makes up for that especially at scale.
If you need £5 that bad, check out other sites from r/beermoney instead and save your account's integrity against faulty researcher detection algos flagging it unfairly (presumably because your friends or even strangers are all 100% certainly on the up-and-up right?), and help keep the pool as reasonable as we can despite Prolific's aggressive onboarding because remember, they care about profit, not you and your ability to support yourself with this platform (despite one of the options in "about me" being willing to work 20+ hours which is legit a part time job in anything that's not "gig work")