Unlike parallel imports, grey imports are brought in from outside the EU.
Historically, these were mainly from the US and Japan, where an EU/UK model didn't exist. Mostly bought by collectors or enthusiasts, these motorbikes could be anything from a classic motorcycle to a brand-new, limited-edition superbike.
Recently, a host of Chinese manufacturers are producing motorbikes cheaply and in great numbers. Even considering shipping and other costs, they can still look like a great deal, and are becoming more popular.
Grey import bikes aren't EU-approved. Before you can register and insure your motorbike you have to get your new ride approved to ensure it meets environmental and safety regulations.
If the motorbike is under 10 years old, it must be inspected under the Motorcycle Single Vehicle Approval (MVSA) scheme.
Once the motorbike has its approval certificate (CoC or MVSA) and assuming all the other paperwork is in order, you can register it.
At this point you get your V5C certificate and you can get number plates made. Then you can finally buy your motorbike insurance before heading out on the road.