Struggling to identify this little bird

Hey there folks,

Spent a very pleasant day mooching around Lackford Lakes on Saturday and noticed this guy flitting through some light shrubs and trees along with around 30+ Long-tailed Tits.

I'm struggling to pin it down to a specific warbler or maybe a chiffchaff but the black tip on the beak is throwing me off the scent.

Much appreciated if anyone can shed some light?

Thanks so much, everyone,

Mark