improve UK GSM Nexus One battery life.

trying to 'find' a 3G signal is the surest way for your battery to drain super quick.
So heres a handy tip which means the phone doesnt waste excess power finding 3G but retains a lookup table,apparently it means your phone is less likely to try and hunt a 3G connection in low signal/power areas.

Dial *#*#4636#*#* and tap phone information.
Scroll down to 'set preferred network type' to GSM Auto (PRL)

remember that sometimes the setting is lost e.g. after your battery dies.
so you have to re-enter it. (youll probably notice the drop in battery then realise lol)

makes a huge difference to my battery life , as well as automatically switching to wireless network when in range of my home.

http://www.google.ie/support/forum/p/android/thread?tid=6a327a95211ac789&hl=en
http://forum.androidcentral.com/google-nexus-one/13037-wifi-turning-off-sleep-mode.html