Wow the amount of traffic is horrendous. That alone is a major plus. Then the pagerank 3 also adds value. boredgames.co.uk : $XXX-XXXX If you are not in a rush to sell, just wait until you get an offer in this range. Odds are, someone will take it.
If you want to sell it with your site you can calculate price of your domain(site). Multiply with 8-10 your monthly income from this site.
.co.uk domain names are very good and the fact that your domain name is short and generic means there is a good amount of potential for it. If I were you, I would hold onto it for a couple more years and you will see big $$$ for the domain name.