I think its a type of shield bug. There are quite a few different species so I wouldn't know exactly which one. If you Google 'shield bug' some similar come up in images.
Thanks for your reply. It looks very like the Pentatomidae group. I'm really pleased to find out what it is.
More specifically it's the Red-legged Shieldbug, Pentatoma rufipes. The adults of this species are quite common at this time of year.
You're spot on. That's so exciting. Thanks very much.