Shadow, was there meant to be missing textures in the demo? If there was, they didn't show up for me, probably because I have them outside of the pk3 file. Thank you for taking the demo though, it did help, and you played around on it for quite a long time.
Ron, I realise that I haven't done any clipping yet. I was always going to do it, I just haven't got up to that stage yet. I'll definitely try and do everything you've said, thanks for the help.
WhoAmI, to test it you need to download the file and put it wherever all your other custom maps are found, this varies so you'll have to look for it yourself. Once the file is in place, you need to start a server by going to "Start Server" on the main menu of Urban Terror and type /map ut4_adv in the console once its going.