No at the moment we don't need an IDP or even two if going through France to Spain. Since I understand that IDPs can be obtained only by personal application at selected Post Offices or by submitting licence and ID information by post, these options may not be available to those already overseas when the 'leave' process is introduced.
As we all - wearryingly -know , this date comes and goes and indeed may never happen. So at a relatively low cost, I suggested just getting IDP/s for about £5 before leaving home and then stop worrying. Given the cost of most Continental tours this is a drop in the bucket, whereas not having one and having to fight with - by then probably unfirendly Continental authorities - could seriously ruin your holiday.
Those of us of a certain age took all this plus Carnets plus Green Cards in our stride without benefit of internet, credit cards etc and thought nothing of it.
Just regard it as another fly that needs to be swatted and do it.