There's no effective treatment available I'm afraid - peach leaf curl is a fungal disease, and there are very few fungicidal treatments these days. Some info on it in the link below

https://www.rhs.org.uk/advice/profile?pid=232

Thank you Bamboo. I only bought the tree last month when it was in bare-twig blossom. On reading your reply and the link you gave I rang the garden centre and am returning the tree to them.

Good idea - it will have been present on the tree when you got it... I suggest you avoid apricot altogether since the tree's been in the garden... plenty of other pretty trees to choose from.

I used to have a malus floribunda which I absolutely loved but it only looked good for a short time in spring and was very dull and rather unhealthy-looking for the rest of the year, so I hesitate to get another. Would one of the prunus family be a safer bet?

Your apricot is a Prunus variety.... what about an Amelanchier of some variety or another, depending how much space you have? White blossom in spring, often multi trunked so interesting shape in winter when leafless, berries in autumn on some varieties, red leaves in autumn on some varieties too. There's a couple of smaller ones that don't have the red autumn leaf colour - Ballerina and Obelisk. Amelanchier lamarkii is the one that goes reliably bright red in autumn, good black berries too, but its a larger one...

Thanks Bamboo. I did buy an A Lamarkii about 3 years ago and it performs as you say except for good autumn colour, which has been disappointing so far. Very beautiful in spring and lovely berries for the birds. I rather fancy something pink or red as I have white in the above, plus a white clematis Armandii. Both were out together this year and a lovely sight, closely followed by a white cherry.

The trouble is, in that link I gave you in my first answer, it does mention that peach leaf curl can affect ornamental prunus.... its a question of whether the fungus that causes peach leaf curl is now present in your garden, having been introduced by the tree you bought... it might not be, and it might be okay to plant an ornamental prunus such as Prunus kiku shidare-zakura or other variety with pink blossom, but I'm not sure.

Thanks Bamboo. I think I'll give it a miss and go for something like a cotoneaster instead, which will come into bloom a bit later and hopefully be trouble-free!