Actually, the last posted UK procedure is about taking at least 20 minutes extra fuel if you are not expecting any delays. More would be prudent. And of course that saying something along the lines that you are low on fuel is not recognized, which is actually true in the whole EU but may be different elsewhere. It is about using PAN or MAYDAY instead which is a much clearer declaration of an emergency than any ambigous sentence about lack of fuel. If one suspects that PAN is not enough, simply use MAYDAY.
However, EU-OPS does require EU carriers to declare an emergency (mayday) at a certain minimum fuel. However most EU carriers have guidance in their manuals that requires a PAN or urgency declaration at another level to create a ladder of escalation.