Can you remember what app it was you're using Mongoose that allows you to quickly turn things on or off, it sounds ideal.

I've just checked, it's a widget called PowerControl, my phone is an HTC Wildfire S so not completely sure it's in the same place, but I had to go Settings->Personalise->Widgets and it was about halfway down the list. It looks like it's an Android standard widget so it should be available on your Samsung. It lets me control screen brightness, GPS and WiFi, disappointingly it doesn't have a button for 3G data but I guess we can't have everything.

Cheers guys, I found a similar widget already installed.

Also my settings seem to be working for the most part, although a few apps have complained about not being able to find a connection/update without me switching 3G back on, I've only used 1Mb of 100Mb so far though so I'm not too worried. really loving the phone now I'm getting used to it.

Install Juice Defender, it automatically disables your 3g connection after a few minutes of the screen being locke and reconnects when you unlock your phone, saves me loads on battery life and I don't have to do a thing.  Very occasionally it doesn't recognise the phones unlocked but its easy enough to disable juice defender and get it to reconnect.

If you want to monitor data try Onavo Count, I used a few different ones in the past but found they caused problems with my phone running slow, using lots of battery life etc so they must have been doing something in the background that was cpu intensive so took them off and put Onavo on about 2 months ago and its been great for keeping an eye on how much I'm using.