if you are moving from an EU country, and can prove that you have owned the vehicles there for over 6 months then you wont pay anything in duty...
Just registration fees...
The customs office will want proof that you lived, and worked in EU, so bank statements and proof of employment, then insurance certs to cover the 6 months, reg certificate V5, that should cover you well..
The customs office are a pain tho, but you should get it duty free if you have all the proof..