It’s totally legitimate, not only is regulated by both the UKGC and the MGA, but it’s also dedicated to safeguarding its players against problematic gambling behaviour. Playzee links to several support resources for players struggling with this (for a full list of these, check out the ‘Safety and Security’ section, above).
Playzee also insist, as a UKGC-regulated casino, that players have to verify their ID and proof of address before requesting a withdrawal.