In fact registering a car in UK which is to be manly used and kept abroad will only make sense if one uses it regularly to travel between the countries. Foreign registered cars may only remain legally in a second EU country for 6 months continuously without being reregistered in the second country.

Extract from EC Directive 83/182
(ec.europa.eu/taxation_customs/resources/documents/com_en.pdf )

A. Determining whether Member States are entitled to tax cars

As Community law stands at present, Member States have wide discretion over maintaining or introducing taxes on cars. The decision as to which cars are liable for national tax is generally linked to vehicle registration. In a communication of 15 May 1996, the Commission observed that an individual cannot be allowed to register his vehicle in the Member State of his choice as this would mean that all vehicles would be registered in the Member State with the lowest tax rates. At the time the Commission confirmed the principle that every individual must register his vehicle in the Member State in which he is normally resident. In most cases it is easy to determine the normal place of residence. Article 7 of Directive 83/182/EC10 sets out precise rules for determining normal residence in situations where the persons concerned are temporarily living and driving in a Member State other than their own. However, as the Commission points out, Court case law holds that the quantitative criterion to which this particular Article refers (having to live more than 185 days per year in a given place) cannot be taken as the main criterion if there are other factors which alter the situation.

Nevertheless the Commission considers defensible the argument whereby, if a resident of one Member State keeps a car which is used fairly regularly at a place in another Member State where he has his second residence, that car should be registered in the second Member State. This approach is also justified in other contexts, e.g. for the purposes of vehicle testing.