HTC Hero :: Google Maps Accuracy - Wireless Network And GPS Settings

I've got a Hero recently unlocked from the 3 network and I'm using a O2 SIM card in it, I have put in all the right settings to get my MMS and Internet working and everything is cool, however I seem to get really vague accuracy when using Google Maps, sometimes "accurate" to within 2400 metres. I think if somebody asked me to guess where they were in the world I reckon I could get closer than that! Anyway from searching the forum I have read a few comments saying to turn off the Wireless network setting in the Location menu and just leave the GPS one selected, which I have done but then even after waiting a few minutes in an open area it fails to find my location.

I know a couple of times with both wireless network and GPS settings enabled it has been accurate enough to be able to pinpoint my location and display the arrow next to the blue dot to show which way I am facing, which is really helpful if you are in a unfamiliar area and trying to navigate to somewhere. Any ideas why it's so poor at picking up my location and are there any apps to help the GPS get a lock? Would this be something that is fixed in the 2.1 update? Which doesn't ever look likely to come out.