Hi Greedyfly - ok - as your rubbish is collected fortnightly it is a problem.
Best thing firstly to do is double bag the rubbish - just get cheap black bags for use with your council bags.
Then purchase a file of citronella - its not expensive but lasts for ages. Available from chemists. Put few drops in a plant spray (the plastic sprayers) - top up with water and spray over the bags where they are left.
Unfortunately cos your rubbish is only collected fortnightly, and due to weather conditions (rain etc) u may have to reapply every so often. Quick spray over the sacks is all it takes. But i can say from experience that cats, foxes, hoggies etc do not like the smell. They will hopefully stay away from the sacks. Meanwhile def get in touch with the council - you pay council tax so hopefully they can help you out. Meanwhile try the citronella - it does deter the little critters from ripping open the bags and making a mess. :o)