Those Chiffchaffs and have local swifts gone now?

Have to say that I agree with Steve, what has been described sound like bog-standard chiffs at this time of year - calls can be quite variable (esp juv calls late in the season). There can be quite wide plumage variation in "normal" chiffs (and in willow warblers) resident or passing through Britain. Made slightly problematic (esp with willow warblers) due to northern Scottish plumage variants with those in southern Britain. Also be aware of birds at this time of year with older warn bleached-browner feathers in some birds possibly along side newly moulted fresher-plumaged brighter birds, plus of course others in mid moult!

The original BTO Phylloscopus field guide by the late Ken Williamson, published decades ago mainly to help ringers sort them out in the hand, to my mind is still the one of best authoritative guides to the various sub-species and plumage variations across the Phylloscopus species range - still a good read!

Chiffs appear to have raised good numbers of young in south Pembs sites I have visited this year - certainly plenty of them about on the Castlemartin peninsula now - many appearing now would fit the descriptions and calls mentioned.

Swifts at Stackpole may finally have left the cliffs now - a bit later than usual. With the weather we have been having lately, quite a lot of migrants may well have been held back.