I wouldn't be shocked if Transferwise goes bust spectacularly
It's got a lot in common with 'multi level' scams. When you get random strangers promoting it online (including here), always but always with a link to click on that should be a warning sign. The 'referral bonus' has to be paid for somehow, and it's the customer who absorbs the cost of their marketing scheme.
I do recommend WorldFirst here, having used it myself for several years. I don't get paid for it though. No 'referral bonus', no 'fees' for doing an exchange and the cash is in a Polish bank account sometimes within minutes. It's saved me a lot of money over the years, especially when I was paid in dollars.
The rather loathesome "Money Saving Expert" Martin Lewis
I quite like him. To a point anyway.