A bird ended up in my kitchen...Help me identify it!

Hello!

I don't know much about birds but this little bird ended up stuck in my kitchen this morning and I'm seeking some help in identifying it. For context I live in Southern England, in an area with grasslands/fields, trees and a back garden with lots of flowers, trees and hedges. I think the bird got in when the dog was let out via the back door leading into the garden. It had a high cry, very melodic and seemed to have collected some material, possibly for a nest (?). The novice that I am, I think it is similar in shape to some kind of tit. Please help!