International drivers Permit if hjave English license?

Perhaps the best answer would come from the respective Embassy or Consulate of the countries where you plan to drive

This should answer your question:
https://www.gov.uk/driving-abroad

given he has a UK license. Some info I found says that if you have a
license within the EU, then you don't need a IDP for countries within
the EU

Yeah, use it while you can... ;-)

Of course the UK still is part of the EU.

One year ago was the VOTE on Brexit. Not the Brexit.

I believe the IDP requirement is not contingent on EU membership but stems from other international treaties, so Brexit should have no impact on this issue. I cannot say this for sure, but I do remember that before Slovenia joined the EU in 2004, IDPs were not required while driving in other European countries, the only requirement was internationally-recognized proof of car insurance, the so-called green card. After joining the EU, that requirement was scrapped as domestic car insurance became automatically recognized throughout the EU.

If you have a modern UK photo licence, that is valid anywhere in the EU. It is also valid in some non-EU countries that have opted-in to the EU licence system, such as Iceland, Norway and Switzerland.
All EU licences are the same format and abbreviations so foreign police can understand them, even if they don't understand the language, no IDP required.

Hopefully Theresa (I-don't-care-about-UK-citizens-living-in-Europe-I-didn't-even-give-them-a-vote-on-Brexit) May won't abolish that benefit as well when Brexit finally comes in 2019.