Slightly complicated, but here are this year's holiday season opening hours:

Kensington will be closed 24th December to 5th January.

Notting Hill, Belgravia and Islington

December 24th 08.00 – 16.00
December 25th closed
December 26th closed
December 27th 09.00 - 18.00
December 28th normal
December 29th normal
December 30th normal
December 31st 08.00 – 16.00
January 1st closed
January 2nd closed (Islington will be open 09.00 - 18.00)
January 3rd normal