Mystery warbler?

A mystery bird has been visiting my parents’ feeder in Hampshire for a couple of months. It looks like some kind of warbler, very pale underneath and brown on top, dumpy and with flesh-coloured legs. I think it looks most like a Cetti’s warbler but I understand that they are very shy and would be unlikely to visit a feeder. Would be grateful for any suggestions. Unfortunately I haven’t heard any calls or song! I will try to add some photos but they aren’t great.

it does’t have the streaky back of a dunnock or female sparrow and the beak is definitely not that of a sparrow. Also well used to seeing chiff-chaffs in my own garden and it lacks the more delicate build and as mentioned the legs are pale.