I've been using Circle since May, also through Prolific. So far no problems, no fees, no issues. I linked It to my debit card and it automatically deposits in my bank account. It is slower than Paypal or Venmo - might take a couple of days - but it works fine to cash out Prolific.
@Dusty Dog, I like Prolific a lot. There are relatively few surveys/studies available but they are high quality and pay well. The site works really well. I tried a bunch of sites like Amazon Turk and various survey sites, and this is the one I stuck with. You won't earn a ton just because there aren't many studies to sign up for, but it's good if you have ten minutes to kill here or there and want to earn a buck or two instead of scrolling on Facebook. It has very user friendly features, like telling you the actual time people are needing to take a study, telling you how it works out as an hourly rate, etc. Like instead of saying you'll get fifty cents to take a study of unknown length, it will say you will get fifty cents to take a study that users spent an average of four minutes on, which works out to however-much per hour. Makes it easy to see which ones are worth doing.