Can anyone identify a bird by my description - please!!

Hello. I am very new to the world of birds and bird watching. I live in Suffolk in a village. I recently saw a bird that I have never seen before in the garden and was actually taken aback by its size, I saw it again last week, so only seen it twice - with a month in between visits. I didn't have a camera to hand.. I have now but its not been back... Anyway - I will get to the point. Its larger, I'd say a pigeon size, its predominantly white/light grey with a electric blue marking on its wing at the top... It has a reasonably broad head...I have only seen it from the side and I desperately hope it returns so I can take pic. I have looked all over the internet and havent seen anything like it... Any ideas??