Further news on the QuickContact screen lock - I've realised that after turning the phone on that I have to manually launch QuickContact otherwise the screen lock won't kick in, so I decided to look for a way to automatically start QuickContact when I turn the phone on.
There is a program called Autostart which does this, but apparently it doesn't work very well and in any case seems to be no longer available at the developer's website, so after some further searching I found a post by zhubajie in this thread on HowardForums which describes how to manually create a startup item.
However when I tried to use the instructions in zhubajie's post to make QuickContact auto-load at startup I found it wouldn't work unless I also had HandyDay 2004 installed (I found I didn't have to have it autoload at startup though). Uninstalling HandyDay 2004 broke the QuickContact auto-start again. I'm guessing that HandyDay changes a configuration file somewhere to tell the P800 to look in the /system/startup folder when it boots up.