I agree with @Ben with the package libreoffice-fresh-en-gb, either using the pamac GUI or the command line.
After installing the above, I’d open libreoffice and check things out before installing anything else, like fonts or spell checker.
You might want to consult this topic on the spell checker. There is a hunspell-en_gb. It might already be installed.
There is also some additional information at the arch wiki on libreoffice.
NOTE: The Manjaro distribution is based on the Arch distribution, which is why users will recommend their documentation as supplemental information.
PS: I actually have libreoffice-still installed.
They are optional for a reason 
>>> pacman -Qi libreoffice-still
...
Optional Deps : java-runtime: adds java support [installed]
java-environment: required by extension-wiki-publisher and extension-nlpsolver [installed]
pstoedit: translates PostScript and PDF graphics into other vector formats
libmythes: for use in thesaurus
beanshell: interactive java -- good for prototyping/macros
libwpg: library for importing and converting WordPerfect Graphics format [installed]
sane: for scanner access [installed]
unixodbc: adds ODBC database support
gst-plugins-base-libs: for multimedia content, e.g. in Impress [installed]
libpaper: takes care of papersize [installed]
postgresql-libs: for postgresql-connector
mariadb-libs: for mysql-connector [installed]
coin-or-mp: required by the Calc solver
gtk3: for GTK3 integration [installed]
kio: for KF5 KDE desktop integration