Quiet bar the Belgian Black-headed Gull back again

I'm struggling with this one. Out for most of daylight hours on both days this weekend. I guess the struggles will, again, at some point pay off but not this weekend. Amongst the gloom and copious amounts of rain yesterday, I saw probably my most distant Waxwing ever from the balcony at Rainham along with at least one Water Pipit, an adult Med Gull and a handful of Yellow-legged Gulls in the stone barges/tip area. Then back in Rotherhithe, I saw absolutely nothing and the Med Gull at Burgess Park hadn't returned and looks likely not to.

River Thames at Rotherhithe this afternoon - looking over to the Canary Wharf complex

Today, in much brighter conditions, I checked a few spots in Greenwich before heading towards the flooded fields and recycling centre at Dartford where I discovered zero gulls! What the heck was happening? But a subsequent text conversation with Andy L made me discover that blustery, bright days mean gulls vanish from Dartford. Anyway, there was a near-adult Yellow-legged Gull off Sara Crescent, Greenhithe while a walk along the Thames at Crossness produced a further 2 adult Yellow-legged Gulls as well as good numbers of Dunlin and Black-tailed Godwits.

1000s of Black-headed Gulls scanned through at various sites today, with not one bit of interest amongst them - except that in the last hour of light back in Rotherhithe, I was re-acquainted with my Belgian friend from last winter as it sat on the perimeter fence of Canada Water: -

Black-headed Gull 7T39953 - ringed near Antwerp, Belgium and once again present in the Tesco car park at Canada Water, Rotherhithe

At least one BTO ringed Black-headed Gull present, but given that I've yet to receive any info on the metal-ringed BTO Black-headed Gulls I read last winter, I'm not sure whether I'll bother with the effort to submit them this time.