I don't understand how you make money, which makes it look like there's going to be hidden costs. If I start at https://www.windsor-telecom.co.uk/memorable-business-number/... and choose, for example, a revenue generating number then go to the payment it says I get a free number that diverts to my phone for no up-front cost and zero monthly fee. So how does that work for you?
Ah, hang on the slide-away at the side says £10, whilst the "STEP 5" says £0. Looks like there might be an issue with your business logic?
On that particular number type the caller pays to call so we take a cut of the call charge, hence revenue generating. Also, only the one and two star numbers are free.