For their basic service of chargebacks, WinChargeback charges £59 up front. Everything else is a percent of recovery. They do have other plans with higher upfront costs, but when you get into things like older credit card payments and wire transfers, there's a lot more work involved in preparing and managing those disputes.
You can always talk directly with your bank about a chargeback. It's free!
Thanks, I'll try to see what plan I can afford with Winchargeback. I did try my bank but they told me MasterCard only disputes within 120 days but Winchargeback told me you get 540 days with fraudulent charges. They told me most of the time they have to educate the banks!