Home Energy - Footpaths Challenge - Checking for Draughts

With my beautiful little hand, I went all around the house checking if there were any drafts. I found one.
Under my front door. I now understand why the corridor is always very cold. So what options do I have to fix this little issue from the least expensive to more expensive options
- Do Nothing
- Make with reclaimed material sa door draught excluder (see pic)
- Change the door sweeps
- Change the front door
Easy busy!

I have to choose one of those options. I might start with the door draught excluder!

What about you?
Did you check for any drafts in your house?
What did you do about it?