I got this in an email today from TFL:
Tube strike
There is planned strike action every Friday and Saturday night between 20:30 and 04:29 the following morning from Friday 7 January until Sunday 19 June. If these strikes go ahead:
Central and Victoria lines could be severely disrupted from 19:00 on both Friday 7 and Saturday 8 January
Customers are advised to check before they travel and use buses or Night Overground services between Highbury & Islington and New Cross Gate to complete their journeys where required.All other Tube lines will run their normal daytime services during these strikes, with the last Tubes in central London leaving around 01:00 and starting again at 05:30. If the RMT goes ahead with its action, services after 19:00 could be busier than normal as customers seek alternative routes.
Perhaps Nigel or one of our London based contributors can give more information.