Thanks to both of you for your advice.
Here's what I did :-
1. Unzipped the switchfile.zip folder on the device & copied the Config folder to the root.
2. Cleared the contents of the LoquendoTTS folder on the device.
3. Extracted the files from Kate.6.9.1.cab, downloaded from
http://www.navitotal.com/forums/showthread.php?924-VOICES-LoquendoTTS-v6.5-(X20). The cab file only contained files.
4. Copied the data into the LoquendoTTS folder on the device.
5. Extracted the files from LoquendoTTS.rar, downloaded from the same page as above. It contained 2 folders (bin and EnglishTE) and files.
6. Overwrote the LoquendoTTS folder on the device with the extracted data.
Selecting the only map in "Switch Maps" re-selects the same map. It does not de-select it.
I can't find the READ FOREIGN LANGUAGE option.
More importantly, only one voice is available for selection (Jane, English UK).
I've re-booted. The only visible difference is that the icons are different.
e.g. the Change Preference icon is still a spanner but now has a light blue box behind it.
Thanks,
Steve.