Works to strengthen or replace Victorian utility pipes before Crossrail construction really kicks off will start on Saturday 16th January and not finish until November (in theory). The eastbound lane of Oxford Street between Newman Street and Tottenham Court Road will be closed for the duration, so the following eastbound routes will be diverted: 7, 8, 10, 25, 55, 73, 98, 390 N7, N8, N10, N55, N73, N98 and N207. Fareham Street off Soho Square will also completely close from 5th January until 2017.
The major alterations that we can see are: the 25 will terminate in both directions at Tottenham Court Road, the 73 and N73 won't serve Tottenham Court Road at all, while the 8, 55 and 98 are going to take so long to get from Oxford Street to New Oxford Street that it'll probably be quicker to walk that bit and pick up another bus. The 7 will do a bit of a dog-leg that's only really going to mess you about if you want it for Great Russell Street. We've mapped the diversions as best we can, and you should take a look at TfL's press release for more information and details of temporary stops.
View TCR Bus Diversions in a larger map