Just wanted to say to anyone who's trying to improve their position changing, I've been playing Christmas Carols by ear and some of them work really well all on one string and so make good shifting practice! The ones I've found best are the following in G major, all sul D, but of course you can do the same fingering on any string.
In Dulci Jubilo
O Come all ye Faithful
See amid the Winter Snow - these 3 start on G
Away in a Manger - starts on open D
hope everyone's having a lovely Christmas break.