Tenatively ID'd as an Iberian Chiffchaff by all who saw it today. It seems to show all the right features with regard to structure, plumage and soft-parts colouration. I have 7 video clips, of which 3 show it singing and 4 are sound track only. These are MOV files and too large to send in to BirdGuides as an email attachment.
Canon 7D and 200 f2.8 lens plus 2x converter (used primarly for taking video together with a shotgun mic.)