So, my guess is that the survey results are fixed for this year, but for future years I think it a good idea to further segment "Other Europe". Right now, its percentage (>16%) is higher than any other save the US and I find that number misleading. Alexa.com suggests that Sweden and Austria might both be good candidates.
According to this query, Spain (which is also "Other Europe" in the survey) beats Italy (which is "Italy") by a close 4458 users to 4456. To mention other countries you have mentioned, Sweden has 5279 users, beating Spain and Italy; Austria has 1789, and the Czech Republic 1804.
The ten top European countries by users are: (in Bold, the ones which appear as individual countries in the survey)
I'd suggest to just ask with the full list when the survey is done, and afterwards maybe group the answers. In that way, the Other Europe countries would always be the ones which are not at the top of the list.