The reason that you may not watch Fox on Demand in the UK is that it is for the American region. You may watch it on Hulu or Fox on Demand's official website, however you will not be able to watch it on a regular cable channel.
Unfortunately Fox on Demand is only available in the United States due to international trade regulations. You will need to hide or disguise your IP address. One site to visit to hide your IP address is www.zend2.com.