Where to put it
A policy only protects you if the client saw it before they paid. Put it where people book: on your booking page, in a pinned post or a story highlight, and in the message you send with a quote. When a client asks for their deposit back, "it was on the page you booked from" ends the conversation far faster than "it is in my highlights somewhere".
Keep it fair
UK consumer law expects terms like these to be fair and clearly explained before the client pays. A deposit that is a reasonable part of the price, kept because a slot was genuinely lost, is easy to stand behind. A large sum kept on a technicality is not. The same goes the other way: if you cancel, the client should get their deposit back or a new date, whichever they prefer, and the policy says so.
Change it to sound like you
The wording is a starting point. Copy it, then change anything that does not sound like you or does not match how you work. If you already have a policy, compare the two: the questions here are the ones most arguments start from.
This is general wording, not legal advice. For the amounts to set and the thinking behind notice periods, read how much a tattoo deposit should be.