Sounds like ignition switch is mashed up inside.Have you disconnected the battery whilst you`re not around your vehicle?I have seen ignition switches smoking away merrily.

Do you own a basic circuit tester & are you competent enough to remove steering column plastic shrouds and bypass your switch?

Just out of interest,do you have a huge bunch of keys wanging around on your ignition key fob as you drive,this has been known to wear a switch out!

Can you give a bit more info,year,mileage?

If you`ve run over or knocked starter on something you could have a problem.Starter is low down and plastic covers do come off and corrosion can set in. Always worthwhile removing any leads +or- and cleaning them up.

Did the engine turn over on the key.

Sounds like you`ve found the problem.Usually when faults appear straight after something`s been changed there`s a link.

You will need to remove all the connectors from the main plastic block and fit individual connectors making sure all connections are secure with no bare wires touching.Then check the fuse box and replace any blown fuses with the correct amperage fuse .