Any hints welcome :)
It's hard to find pictures of willow warblers from similar angles, but here is one that looks similar: www.thetimes.co.uk/.../nature-notes-willow-warblers-are-singing-5t5rkntwrqr The eyebrow stripe seems a bit more marked than it is on a chiffchaff (in general). But it isn't a million miles away from looking like a wood warbler...! Not sure if you have those there, though, doesn't look like the right kind of woodland, maybe.