I would welcome any advice on the identification of this warbler, seen when the fog cleared at Al Rafa'a (just along the coast from Dreamland in Umm Al Quwain) on Saturday morning. Visually it was a small, distinctly grey bird with whitish underparts, long-tailed, short-winged and quite flighty; settling only for seconds and then off to the next bush. I didn't see any obvious pattern of tail movements and it was silent as it moved around. I had heard 'tchk' calls close-by earlier but assumed this was a Lesser Whitethroat seen earlier, and couldn't certainly attribute tha call to this bird.

My first thought is Chiffy, Steve, but I'm totally thrown by what appears to be white outer tail feathers! Any other pics?
Thanks for having a look at this, Mark. I only have two poor photos taken from distance and heavily cropped. See below. I've seen a lot of Chiffchaffs in the last few weeks and it didn't 'seem' like a Chiffy (not very objective!). It was flighty (moving from tree to bush) but it didn't have any jerky movements or do any tail flicking. I thought of Eastern Olly with the pale tail edges, but it didn't have the characteristic downward pumping of the tail.
Sykes's possible, Mark? Or just a very worn Chiffchaff?
Sykes' was one of the first things I considered (and the only other possibility I can think of), but is there anything to suggest that it's not just a worn, greyish Chiffy? Legs are dark, there's a greenish cast to the mantle and rather more enhanced super on the flight shot.
I'm not convinced 100% either way, to be honest.
Yes, it doesn't look quite right for either.