Hi Chris
Unless you have turned off notifications on your PC/Tablet etc you should receive a message saying who has liked your post.
I received one today.
Message headed "Someone likes your post" 'Skydive130 liked Painting commenced! Looking good. Must be a new type of paint with that overnight finishing technique!'

Stephen (Fireboat) posted a reply in May this year on the Forum under 'anything website related - Private Messages'.

"Private messages from other members cannot be deleted, only marked as read. You can delete private messages you send, which will also delete it from the recipient, but it's not advised. As soon as you send a PM an email will go out to the recipient in any case which of course cannot be retracted...

You want to do this to tidy up your private messages page?

Stephen"

If you need further clarification I suggest you send Stephen (Fireboat) a personal message.
Dave