EMS is indeed the Express Mail Service, the Chinese Post Office in effect, rather than an international shipping company like UPS. EMS is generally quick and not too expensive, but currently has severe shipment restrictions because of the Olympic Games. UPS are relatively unaffected by the Games, but are much more expensive. EMS has a direct tie-in to the Royal Mail/Parcelforce, so an EMS tracking number will work on the Royal Mail/Parcelforce site to track delivery within the UK, which is very useful. The handling charges that the Royal Mail/Parcelforce may apply for handling customs clearance, duty and VAT liability are also more reasonable than those from the likes of TNT, UPS etc, in my experience.
If you motor kit doesn't contain a battery than EMS will probably be able to ship it OK, the current problems in mainland China are largely to do with the shipment of hazardous cargo whilst the Games are on. Some vendors are trans-shipping through Hong Kong, as the restrictions are less stringent there at the moment. Taiwan may well be OK too, as it's not part of the PRC, my guess is that it depends on the route the package takes.
Jeremy