No chance are you OK. IF ,and I say if, Playboy found out then they could easily issue a DRS. Mt advice would be to get Nominet to cancel the domain and then re reg it in different name ??.
DRS is the dispute resolution service that Nominet offer to complainants to try and grab a name back that they think they are entitled to whether because they have a trademark or other reason. Best way to avoid drs is not to use the domain and not to approach any buyer. You have to really think to yourself before regging any name "what am I actually registering this name for ?. Am I regging it for traffice ONLY. Am I regging it to sell it ?. etc etc " . I realised that it is pointless registering a TM name unless is gets LOTS of hits as you will never ever sell it to anyone as no one will buy it.
Playboy are notorious for protecting their brands. It isn't a DRS you have to worry about (you'll only lose the domain there) it's legal action with damages that is a real possibility. I would delete this very quickly if I were you and hope they don't ever come across this thread.