Fingers crossed

I get very sad when a bird flies into a window, especially when it is such a rare visitor as this! I’m not sure whether it is a Chiffchaff or a Willow Warbler, I’m leaning towards Willow Warbler, but either way, not a bird I have ever seen in our garden before. I saw, and heard, it fly into one of the porch windows, there are plants on the window sill and a hanging bird which I had hoped would stop this from happening but sadly not. It sat on the ground for a long time and I guarded it from afar in case either Leela, or a squirrel, took an interest in it (I’ve witnessed a squirrel eat a stunned bird before and it’s not pleasant!). After some time a big wood pigeon wandered over to it and, as I got up to scare the woodpigeon, the little casualty was scared into taking flight too. Hooray, at least it got up off the ground and into some bushes. Fingers crossed it makes a full recovery and is able to migrate before the winter.
If anyone can identify it properly for me, I would be very grateful.