The C2161 No1 Williams was indeed made in China as well as the UK. The Chinese made version, in a slightly darker red, is C2161W and was part of Set C1035 Formula 1 and paired with C2220W Jordan No9 Hornet liveried car. The Set was released in 1999 at the time Hornby was part-way moving production to China.
C2161W was found to have three versions. One with a Castrol logo on the front edge of the side pods on both sides and the other with ‘Williams’ not printed on the air-intake above the driver’s head. Sometimes a tampo operation is missed out simply because the ink ran out during the tampo print production run. Several dozen may have passed through the run before, if at all, it was noticed that the ink plate well was dry. Even if noticed the production operative may have turned a blind eye rather than re-run dozens or hundreds through the tampo print machine again
However, many productions runs of cars for Sets did have reduced printing operations to reduce cost.