How can I configure OS X Mavericks to use a UK PC keyboard layout?
If the British PC layout from apple is not right, some alternatives can be found at
http://liyang.hu/osx-british.xhtml
After downloading alternatives from the link suggested in Tomg's answer, I realised while making them active that there is already a "British - PC" layout installed by default.
To activate it was Settings->Keyboard->Input Sources->Plus sign & find it from the list, and then click the input source icon in the menu bar to select it.