Think it sounds fun actually, oddly erotic and she looks hot. It’s the £60 that would put me off, as ultimately you’re not getting sucked off or fucking her - you’re only really playing to watch her play and wank into her knickers. Interesting kink but not worth £60.
Quite like playing with their underwear though. A while ago, an SP took her thong off and wrapped it around my cock (off the cuff) and then told me to leave it there while I fucked her. Always sticks in my memory as was oddly hot.