Naim may be able to replace it for around £150 plus courier charges. You have to do this via your dealer.
An alternative is that you can buy a screen yourself on eBay from a supplier in France and fit it yourself. You have to get really intimate with the Unitilite internals to do it, but you don’t need to solder anything. (I have done this myself and the first time you do it will take some hours, but the second time would be much quicker!) The screen on eBay is around £110 (last time I checked, but I haven’t checked the price recently).
David, thank you for your prompt response and suggestion. I don’t know if I would fell confident to carry out the repair myself but will certainly look into it.
I ordered the screen from the company in France. It came with explicit instructions and so decided to replace it myself. It was fiddly but managed to install the new screen.