The CAA don't recognise these safety pilot hours as others have said.
What you put in your log book and later declare as your total time is entirely up to you, but under JAR these hours are no more real to the authority than hours you log as a passenger. I'm not trying to be sarcastic or even make comment about this being the right approach or not, just stating fact.
If you log them and then later down the line have to justify them, then you're going to find yourself in a difficult position! In addition, if you are applying for a professional licence at some stage then if you include these hours (and I can't remember what they ask for on the form) you will be telling pork pies to the authority...probably not such a good idea!