Guys just include a cover letter, it won't be thrown in the bin that's for sure, it shows initiative too. I attended a selection preparation day and they also encouraged including a cover letter even if not specifically asked, you're trying to sell yourself so seize every possible opportunity to do so.
And they are flexible, I emailed them after submitting to even update my CV and they allowed so, also offering the chance to update/edit my cover letter. So it's never too late, they are very flexible and understanding if last time is anything to go by.