Door handles, fixtures and fittings, and other hardware don't have to match exactly, but they should blend together to make a harmonious space.
Replacing the door handles will cost anything from £10 upwards per door (I use Carlisle Brass for quality and price point). It's one of those details that needs to be done. Hinges need to match, too. That goes for the kitchen as well, if they show on the door.
If you have a home where the outside door hardware can't be changed, you can often update the inside of the door to coordinate with your decor.
Investing in this important detail will make a big difference that you'll notice immediately.