great site! really like it.
you could try doing a prize draw every monthly, something like win a ipod or xbox and sumit it on sites like:
www.ukcompetitions.com
www.loquax.co.uk
you should be able to find 20 odd if u search in google etc then have a good landing page a bit like:
http://www.preventx.co.uk/compenter.aspx
you should get around 12000 extra hits per month and then 6000 opt-in email address, which you can email in the future, but I lot of these people are competition junkies, who might never buy ur services but will bring in traffic. total cost £200
The other option you could try is doing a funny or rude link, and post it on forums, but it has to be good quailty otherwise people won't forward it to there friends etc.
her's another example:
http://www.preventx.co.uk/chlamydiatest.aspx
option 3 is the good old press ads, you could try, fhm, nuts, loaded etc, if you ring up and ask for any last minute spaces. A credit card size ad in the back often has a rate card price of £1200 - £600 eg 64mm x 30mm but if u pay upfront etc and screw them down, u can pay £150 - £200, but you can't tell if they work.
sometimes things like have a promo car could work, eg a smart car is £150 a month on contract hire, you can spend that a day on google then park it out side a big uni in the day and near bars, nightclubs at night, but you have to drive a smart and sign up for 20 months and cover it will logo's etc
But I did it for a cheque cashing shop and worked well. (mini cooper and a smart)
good luck
Tom