It could be a theme or plugin issue
Deactivate all but bbpress and see if this fixes. if it does, re-enable one at a time to see which is causing the error.
If plugins don’t pinpoint the problem, as a test switch to a default theme such as twentyfifteen, and see if this fixes.
Also can you tell us what language you are set to in
Then come back
After some Googling, I think it might have something to do with my character set settings or coalition? But this is where it’s troubling for myself.
For more information, I’ve checked my database as the ‘Â£’ is actually being stored (i.e. it seems to be an input issue rather than retrieval), so it’s a problem between inputting and saving.
My wp-config.php shows:
/** Database Charset to use in creating database tables. */
/** The Database Collate type. Don’t change this if in doubt. */
Whilst the post tables in my database are here : http://i.stack.imgur.com/452XL.png