Katie writes
I have discovered I have four potato plants in my rather small garden
that have grown from potatoes in the compost - we only have two small
beds and put almost a whole dalek full of compost on the two earlier
in the year, clearly some of it wasn't rotted.

I have done nothing with them, but am wondering a) is there any point
in doing anything b) if so, what (I seem to have a vague idea about
shoring them up or something like that!)

You need to keep any tubers covered with earth else they go green and
poisonous and, in theory, earthing up encourages more tubers. As long as
you put some earth on any that show through the surface, you'll be OK
even if you don't earth up.

and c) if I am likely to get
any potatoes from them and if so, how will I know they are ready?

Feel around with your fingers and see if they're large enough. If you
wait till the foliage dies down they should be ready, but sometimes
they're ready before that. Don't expect much more than a meal form each
plant, but they generally taste wonderful, so it's a special meal.

--
Kay