Android updates for Nexus bought from Amazon
Galaxy Nexus goes by variants such as yakju, yakjuxw, and takju. However yakju and takju will receive updates directly from Google. While the rest will be receiving from Samsung or probably network provider.

The difference between yakju and takju is that takju has Google wallet while yakju does not. Takju can only be purchased from Play Store.

I assume the one being sold directly from Google in the UK is the same one offered at Play Store which runs takju while the one on Amazon runs yakju.

In term of phone hardware they are exactly the same.