British English thesaurus for openoffice.org v2.

To install:

Open the openoffice writer, and choose tools-> options. Under
openoffice.org on the left hand side, select paths. Make a note of
the path for "Writing aids".  Close the openoffice program, and any
quick launch program that is running.

Switch to a user with permission to change the installed files and
change to the directory noted above. Change to the subdirectory ooo.
Copy the files th_en_GB_new.dat and th_en_GB_new.idx to this
directory. Edit the file dictionary.lst and remove the line that
starts:
THES en GB 
if it exists.

Add the following line:
THES en GB th_en_GB_new

Restart openoffice writer. From tools->options select
language settings->languages
Select English (UK) for every option where it is allowed (User
Interface may not be available). Now click Writig aids. Make sure
that all the options in the first box are ticked, and click the Edit
button nearest the top. Select English (UK) for the language, and
click close, and OK to return to the document.

To test the thesaurus, type colour in, and CTRL+F7 (or
tools->Language->Thesaurus) for the thesaurus.
It should come up with a list of words, none of which is color.
If color is an option you still have the original thesaurus. Click
the Language... button and select English (UK) as the language.
It should work now.

If you have problems try posting in the forums - Navigate from
brit-thesaurus.sourceforge.net