/usr/lib/aspell/british-wo_accents.alias is in aspell-en 6.0-0-6ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | # Generated with Aspell Dicts "proc" script version 0.60.2
add en_GB-wo_accents.multi
|