I was under the impression that when insuring with a performance car specialist (eg moley or sky) then an import would cost no more than a UK car.

Are you sure its the fact that its an import raising the cost and not your post code or driving history.

 

I had the same trouble myself imports were coming in double the price of a uk model

 

Sourcing of parts is probably one reason.
Cost of repairs are presumably a lot more.

I just ordered a part from Japan for my JDM.
It cost £23, plus £12 express air freight.

Once it was in this country and in Parcelforce's hands they informed me that there was another £20-odd in Customs and 'Admin' charges.