Buying foreign car in Ireland

Bykobap wrote: »

So a car is to be privately bought for a lot of money tomorrow if it's mechanically sound, it's Polish registered and is in Ireland.

It's most likely illegal to sell Polish registered car in Ireland. Surely it's illegal to be done by Irish resident person, and I'm not sure if it's illegal to be done by foreign resident or not.

Now this car is to be driven across Europe towing an Irish camper by Croatian citizen. Polish registration(insurance) expires during this month long touring of Europe.
Whats the craic with change of ownership of Polish registered car whats the procedure?.

In Poland new owner needs to visit city/county office to have car registered in his name. But while the buyer is surely not Polish resident, that's not an option.
Buyer should register it in the country where he/she is resident in (whether it be Ireland or Croatia or other)

Car wont be driven at all in Ireland apart from leaving the island in January for good, is VRT a must or what?.

Legally yes. VRT is a requirement. Enforcement is another thing though.

Can he tow an Irish camper on Polish reg car with Croatian licence?.

There's going to be big issue there.
Irish caravans don't have their own registration numbers.
As Ireland have no system for registering trailers/caravans all those from Ireland would be probably treated as unregistered on the Continent (except from those towed by Irish registered cars) and therefore are probably not legal.
Like I can't think of what number plate would you put on Irish trailer towed by Polish registered car.

What paperwork is required to register foreign car from one country to another etc.

Usually registration certificate from country of origin (in the last owner's name).