The reality is your NHS hearing aids, which were provided free of charge, would cost you a great deal of money to buy privately… tbf, the fees for replacing them if lost or damaged are not a lot by comparison.
What a great community we have here at TheAnswer Bank!
Thank you all who provided information which was most helpful.
I've reported the loss to my NHS provider and they have just called me back to say they will be sending the appropriate replacement shortly. No mention of cost so far but I'll keep you informed of the result. Thanks again to all.