This is a very tough call indeed, and I wouldn't advise you to tick it as anything, just chalk it down to 'the one that got away'.
However, I'm about 90% it's a Marsh Tit.
In pic 1 there is no hint of a pale wing panel, although the cheek looks good for willow.
in pic 2 there is a wing panel, but if you look at the angle of the bird then you've got the secondaries edge-on to the camera. Marsh often shows a wing panel at this angle as they too have pale secondary edges (though thinner than willow, but you'd not see that from this angle).
You can also see that the bird is very puffed-up and rounded, which would also give Marsh a bull-headed appearance in that pose. Also, the underparts aren't warm enough for me, although the lighting isn't good.
pic 3 appears to show a straightforward marsh tit. Good demarcation between the white cheek and the dusky side of the neck behind the ear covert (though lighting's not helpful again), cool colour tone to the underparts, marsh tit jizz.
If it wasn't for pic 2 and that apparent wing panel, I'd say 100% marsh tit, but pic 2 does look a bit willowy. However, when you see how that panel disappears in pic 1 and the bird looks like a good marsh tit in pic 3, then it certainly leans very strongly to Marsh.