Making some sense of it…. and planning your weekends !

If like me you are confused as to why Wales are playing Northern Ireland and Croatia Portugal, I can only sympathise. It has taken me a good half hour to work out this 3rd place system and even then it relies on accepting a pre-arranged formula in need of further explanation. 

See table right: The top four best 3rd placed teams were in order: Slovakia, Ireland, Portugal and N. Ireland. This meant groups, B C E & F provided the winning line. So that's all we're concerned with in this table. 
Only Winners from the groups A,B,C,D would play a 3rd placed team, so column WA (winner A: France plays 3rd place in E: Ireland. WB (winner B: Wales plays 3rd place in C: N. Ireland. WC (winner C: Germany plays 3rd place in B: Slovakia. And WD (winner D: Croatia plays 3rd place in F: Portugal. Phew, I need a lie down now.