In reply to leeoftroy: I've bought and sold quite a few items on here, without any issue. Only had one item never arrive, and the money was refunded quickly via PayPal. I don't think for one second that it wasn't sent - I suspect Royal Mail lost it.
As mentioned earlier, you get an impression from previous posts and from email contact whether the person is likely to be genuine or a wrong 'un.
I wouldn't be concerned if a poster is only using the site to sell kit, rather than taking part in other conversations - the way they use UKC is up to them, and they'd soon be outed if sold kit wasn't arriving. However, and brand new user trying to sell kit may be cause for concern.