I bought a ticket from one street and parked it in another street.

They've issued me this PCN saying that the Officer did not observe a valid Pay and Display ticket.

And that the ticket purchased falls within the Outer Zone, but I parked within the Inner Zone.

I've followed links to Money Saving Expert for advice, but can't find help on this particular case of events.

Is it worth me appealing.

If the nearby signs where you parked weren't adequate, ie it wasn't clear that tickets purchased in one street were not valid in another street round the corner then, yes definitely worth appealing

I successfully appealed against driving in a bus lane because of bad sign-age (yes, it was a genuine mistake before anyone asks!)

Why would you buy a ticket in one street and park it in another street?