Med Gull or BG Gull Juv?

Spent a few days on Isle of Purbeck beginning of this week and spotted this gull by the side of the road on Studland that goes to the ferry to Poole. I am not sure if this is a Med Gull or a BH Gull juv. 

I know there is a Med Gull colony in Poole Harbour and also BH Gulls, a little confused by this one?