If there's a no deal come the 29th of March, you'll be required to have an IDP to drive in Europe, be it in your own car or a hire car. Whether car hire firms will insist on seeing your IDP when you hire is another matter, but we'd suggest getting one just in case. They cost £5.50 and you can get one from the Post Office but be aware that there are in fact three types (they don't like to make things simple). The 1968 IDP covers the majority of EU countries but you'll need a different 1949 IDP to cover driving in Cyprus, Iceland, Malta and Spain. A 1926 IDP is required to drive in Liechtenstein but you don't need an IDP to drive in Ireland.