I go onto Google, type my website name in and the search result shows my meta description has been taken over by spammers (I'd recommend everyone to check for the same thing)

Any idea how I can get it back to the description of my site and not an advert for pills?

What do you mean?

So when you go to google.com and type in your website name (e.g. 'travelfforums') and the results come up, instead of it saying 'travelforums.co.uk and then 'travel forums for discussing all things travel in the Uk and beyond' it says 'travelforums.co.uk and then 'ED is not something that may last forever for men living in Malaysia. Just order kamagra malaysia - generic sildenafil citrate for cheap price and obtain awesome pills'

If google is picking it up, its on your server more than likely. So when you go to the page and view the source, is it there? If so, check your meta tags, check for any files that may be rewriting your meta tag.

 

Yeah I think something is server side writing it like you say

Not sure how to spot it though

The actual forum is fine - so must be a file on the server