X-ray film cannot be put into your household recycling bin. Contact your hospital to see if they will accept it for recycling. The film contain small amounts of silver so there is real value in recycling it.
If the hospital won't accept the x-ray film, try the City of London Hazardous Waste Service (opens in new window) or search online for a (private) recycling company to take it.
If you are unable to recycle the x-ray film, it can go in your general waste bin.