More analysis shows:
Complete overlap of WRC15 band for all 13 countries with WRC15
Latvia (CW-Dig modes only up to 800Hz wide),
Portugal / The Azores,
plus Croatia, Iceland, Norway, Slovakia, Denmark/Faroe Is, Hungary, Netherlands, Somalia.
Other countries whose channels or blocks overlap are as follows:
Czech republic overlap channel in band – 5362
Israel overlap channel in band – 5357
Romania overlap channel in band – 5363.5
UK overlap blocks in WRC15 Band – 5354-5358, 5362-5366.5
Macedonia – may have an overlap however the specific 15KHz blocks are not listed in Wikipedia.
IARU region 1 countries that definitely DO NOT have an overlap are:
Therefore I would recomend those in countries with the WRC15 Band to use 5362 KHz(OK+G), 5363.5 KHz(YO+G) & 5357 KHz(4X) for band overlap with other non-WRC15 countries (as well as other WRC15 countries of course).