Thanks for your responses. The foundation said I should hand over the WP to them and they will cancel it on the day I leave. It didn't sound right based on what I have read in this group, so I went to the labour office today to ask and they said I should leave first, and the WP should be cancelled after. That's why I'm left a bit confused.
I don't have a 'last working day' as such - it just depends on the day I exit.
But you're saying, current policy is that I need to cancel the WP before exiting and also cancel the extension?