.UK is a weird TLD. For example, transfers between registrars are free (you don’t have to extend the domain by a year are transferring), and there’s a “push” transfer system instead of a “pull” system. You also have the ability to do certain management of the domain through Nominet instead of your registrar. Unfortunately, none of this seems to work very well and it took me months to successfully transfer my .UK, I even tried using Nominet’s paid transfer option to force the issue and it still failed over and over (although I always got a refund). Eventually it just worked for no apparent reason.

.win is fine. It might be on some extremely aggressive spam filters but it’s unlikely to affect you much.