This is one I took last April and searched for it's ID http://365project.org/mejbronant/365/2012-04-17. It's a Hawthorn Shield Bug but I quite like Bernadette's suggestion. The one I saw demonstrated some aggresive behaviour towards me!! But I was invading it's space to get a macro shot!
@mejbronant Thanks Mair for taking time to reply. This one was very quiet and didn't move while I got close. The light wasn't ideal as it was coming from behind the leaf. Your shot was much clearer.