Rough ballpark, about £40k each. Depends enormously on hours, condition, avionics fit, when the next CofA renewal is due, and when the next engine overhaul is due. Also, PA28s especially vary a great deal, and model will make a big difference.
You can compare prices and specs by buying a current issue of "Pilot" from WH Smiths and looking at the thousands of classified ads in the back.
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