Hi Sara,
The GEO-IP redirect isn't an approach I favour.
As Google normally crawl from a US IP it can cause indexation problems.
As such I prefer something like cheapflights.com implement - if you visit cheapflights.com from a UK IP you are pushed to this international choice page - http://www.cheapflights.com/workers/profile-select.aspx?sref=CFUK&redirect=GeoIP&geoip=GB&cfref=CFUS&spt=Home&rp=/
This allows user to select the appropriate site (nicer for users) and allows both versions to be crawled.
My recommendation would be to implement something like that rather than a hard redirect to a specific language version.
I hope this helps,
Hannah