There are 2 routes to go down:
Route 1: Dont import the car and leave it on English plates...... Officially this is of course a bit of a no-no. The rule is that after 6 months a car should normally be imported - however after nearly 7 years of running UK plated cars abroad im yet to have a problem! Im not saying they cant occur, however the chances are so small they are worth the 'risk' IMO.
There are brokers in the UK who will now permanently insure a car outside the UK with no quibbles - Stuart Collins is a good example. Even mainstream companies such as eCar Insurance give 365/365 cover these days. You do NOT need to take the extra fully comp packages most insurers offer if you dont want to. 3rd party cover provides 365/365 European cover by law, its just the insurance companies dont like to tell you that!
If the car is only going to be used as a weekend toy id be even more inclined to leave it on a UK plate and take advantage of the cheaper road tax etc.
Route 2: Importing......
You have to pay luxury tax (BPM) when buying a new car here in NL - BPM has to be paid at a depreciated rate when importing older cars - as a rough guess id expect to pay around €1000 in import taxes on the GTV (may be a bit less if you are lucky), plus another €200 or so in admin costs and the Dutch MOT (APK).
HOWEVER: If you are moving here to 'live and work' and your employer can back you up, you are entitled to import one car tax free as part of your personal possessions - im not sure on the exact rules as I have not gone down this process myself (my Dutch cars are on special plates). I think you need to have owned the car in the UK for 6 months beforehand, and are prohibited from selling in NL for 12 months - a bit of Googling will reveal all I expect.
Luckily a GTV is very easy to import - mainly because it already has two rear fogs, the front lights are very easy to swap to LHD dip models and the Speedo is already in KM, so basically budget about €150 for new headlights and you are set. You will need the CoC (certificate of conformity) from Alfa, usually not hard or expensive to get hold of, plus the UK MOT and V5. You simply go down to the local RDW office here in NL, tell them you want to import the car, they give you a one day temporary Dutch plate, an appointment and ask for money. The will then have a Dutch MOT, a quick inspection and you are off..... its usually a quick process.
Expect to pay about €650 PA in road tax and insurance should be about the same price as in the UK, may be a little more....... Servicing/specialists in the Amsterdam area should be no probs at all, theres a big Alfa scene here, but expect to pay a LOT more than UK prices for parts etc. I always buy in the UK these days.
The other advantage of importing is that the car is worth a LOT more here, even as RHD id imagine you would get 2-3x the UK value for the car.
HTH, any more Qs just ask - its quite an expansive subject to cover in one reply...!
-1998 916 Spider 2.0TS Lusso-
H&S Corse stage 1.
CATCAMs stage 1 cams with Savali custom ECU remap.
305mm discs with 166 4-pot callipers.
Ragazzon exhaust mid section.
Biscione Racing 2x70mm rear section.
17" Zender Siena wheels with 3mm rear spacers.
etc etc etc!