Ahh okay!
I’d say just to change the rates on whichever site you advertise and then when they ask for a booking refer them to the site, and polite as pie ask them to read over the new rates.
If they’re regulars they may not want to see someone new? So they’ll be happy enough with the new rates.
However ! Your site rates I’m guessing are your typical and you aren’t wanting to higher your rates at all? Sorry I’m confusing this haha.
I think the best thing to do is to just tell them the rates when they ask for a booking.
“Can I see you again this Friday? “
“Yes that’s fine, (please see my profile for the rate for that session), (that is £150 for the hour)”.
At the end of the day, it’s your body, your service, your business, who can charge whatever you want to. If you (and you don’t seem that bothered about) aren’t worried that they’ll not book again, then it shouldn’t be a big deal to just tell them that they’ll be charged the original rates from now on.
Xx