Unidentified bird on heathland

Unidentified bird on heathland

Observation - Unidentified bird on heathland - UK and Ireland. Description: I appreciate this is not a great picture. However, if anyone can point me in the right direction I should be pleased. A small bird seen on gorse on the Ashdown Forest area of Sussex. Similar birds definitely seen were Dartford Warbler, Whitethroat, linnet

I appreciate this is not a great picture. However, if anyone can point me in the right direction I should be pleased. A small bird seen on gorse on the Ashdown Forest area of Sussex. Similar birds definitely seen were Dartford Warbler, Whitethroat, linnet, stonechat, chiffchaff, wren. Thanks, as always for any help you are able to give. Update: 2nd picture now added but I'm not sure it will help! Thanks anyway.