Probably UK, because iOS marketshare in UK is very close to 50% (52% Android, 46% iOS [1]). For curious, in some countries there is much more Apple iPhone users than Android users, like in Liechtenstein (58% [2]) or Monaco (64% [3]).
[1]: http://gs.statcounter.com/os-market-share/mobile/united-king...
[2]: http://gs.statcounter.com/os-market-share/mobile/liechtenste...
[3]: http://gs.statcounter.com/os-market-share/mobile/monaco