Vibrating Accelerator/igniton Lock?

[Poppy]

Hello, when I put my foot down (even just a little), specially when going from a low (automatic) gear, uphill for example, there's a vibration near to the accelerator, but underneath the car somewhere. It's as though something is not quite taut. Does this make any sense and any ideas?

Also, have suddenly had great difficulty in getting key in ignition lock and then turning on. Seems to me to almost certainly be the lock not the key, because it's the same with each of three keys and they're not perfect matches. Would anyone know if there's a remedy other than a new lock and key, or barrel as I think they're called?

Many thanks

Neil C