Our SIN based cabin crew, called ICC (International Cabin Crew, as they are based at one of the International bases) will fly LHR-SIN, SIN-LHR and some of the Chinese routes. Now that MF operate the LHR-SIN-SYD they will fly alongside WW and MF crew, though not on every departure from LHR operated by MF, as MF have employed Mandarin speaking crew based in LHR.
ICC bases are located in SIN, HKG, NRT, MEX, GRU, BOM, DEL, CAI and BAH. Most wear the normal BA uniform, with the exception of our Indian ICC's who wear a variation. Generally 1 or 2 per aircraft though with MF there will be a language speaker but they will be LHR based, with the exception of some SIN flights and those to KWI, AUH/MCT who have 2 CAI based crew on.
Hope this clarifies!
Kind regards
D1L