ID this LBJ... is it a hybrid?

Can anyone help with ID-ing this LBJ, seen in early March in central Newcastle? It's a fairly dull brown-grey, roughly sparrow-size, with a paler vertical stripe on its chest. I ran the audio through Merlin and it appears to suggest blue tit - but clearly the colouring is not right... might this be a hybrid of a blue tit with... another tit? Thanks in advance for any suggestions.