Hi - I don’t know if you’ve tried these links, but I have been using them for the last week without experiencing the stutter that the “raw” links exhibit in Volumio (although not in VLC or Foobar2000).
As far as the Volumio buffer setting is concerned I usually have mine set to 12MB without any problems. However I have just tried setting to 2MB with no noticable difference!
Good luck - and keep trying!
Michael
BBC Radio 3
http://lstn.lv/bbc.m3u8?station=bbc_radio_three&bitrate=320000
BBC Radio 4
http://lstn.lv/bbc.m3u8?station=bbc_radio_fourfm&bitrate=320000
BBC Radio 4 extra
http://lstn.lv/bbc.m3u8?station=bbc_radio_four_extra&bitrate=320000
BBC Radio 5 Live
http://lstn.lv/bbc.m3u8?station=bbc_radio_five_live&bitrate=320000
BBC Radio 6 Music
http://lstn.lv/bbc.m3u8?station=bbc_6music&bitrate=320000
BBC Newcastle
http://lstn.lv/bbc.m3u8?station=bbc_radio_newcastle&bitrate=320000
BBC Berkshire
http://lstn.lv/bbc.m3u8?station=bbc_radio_berkshire&bitrate=320000