The UK dictionary should be installed as the package myspell-en-gb. Previously to install the English (UK) dictionary one had to:
$ wget http://dict.progbits.com/en_GB.zip $ cd /usr/lib/openoffice/share/dict/ooo $ sudo unzip ~/en_GB.zip $ chmod u=rw,go=r *en_GB* $ sudo zile dictionary.lst DICT en GB en_GB $
Then in openoffice enable the GB dictionary and disable the US dictionary. Go to ToolsOptions. Language SettingsWriting AidsEdit. Turn off US spelling (keep US hyphenation) and then English UK and turn on spelling (and US hyphenation). Then in Language SettingsLanguages choose English UK.
The thesaurus with the GB dictionary does not exist. There is a US thesaurus though. To make it available under GB add the following line to the end of /usr/share/myspell/dicts/dictionary.lst:
THES en GB th_en_US