I think if I was still using a Galaxy Nexus, I wouldn't feel a pressing need to upgrade but I'm not so sure about the Nexus S.
What version of Android do you have running on your device and if it is the latest (Jelly Bean), how is the performance ?
What version of Android do you have running on your device and if it is the latest (Jelly Bean), how is the performance ?
The early 4.1 kept eating the battery but 4.2 is OK as long as I switch of wifi when out and about.
And I don't think UK carriers have any meaningful control about when Android OTA updates are pushed out?