Probably simplest to use a 555 timer circuit for controlling the relay. I believe Velleman also make a timed relay kit, which may do what you want.
You can alter the mark / space ratio of a 555 timer, it doesn't have to be 1:1.
Given rocket01 self confessed lack of electrical knowledge I'm not sure this is going to be much use to him!!Beat me to it. There's a book by Babani publishing called something like '555 IC Circuits' that tells you all you could ever need to know about using a 555.
Given rocket01 self confessed lack of electrical knowledge I'm not sure this is going to be much use to him!!![]()