suffering from a very tender swollen foot

I would agree that if you haven’t injured your foot in any way a walk in clinic would be for the best - sorry about the ‘walk in’ bit obvs walking is painful right now.
If you have a walking stick use that for now and compensate with your other foot if you can.
Hoping you can resolve this sooner rather than later.

Is the foot red and feels warm, infoman?

If it is then you need to see the GP asap, ie today, as it could be cellulitis and you need antibiotics.

If it's from a sprain or something chronic then crutches might be better.

If there is no obvious reason for the swelling or pain you may need to go to a walk in centre.

Wouldn't a crutch be better?