Cannot seem to figure out what this birdy is ...

Hi all ... I took this photo in my parents garden ... I've been bird watching two weeks now and this is the first bird I have struggled to identify ... I thought a chiffchaff but it didn't have the distinctive white "T" ... the only bird I could find in my book that had that kind of marking was a chaffinch ... if it was a chaffinch it could only be a female but the thing that's making me doubt it is that the book image shows another white section above the "T" but as you can see here this bird doesn't have it :/

Any suggestions ?

Thank you :)

Thank you Sila :)

My photos can be viewed here