You have the dreaded leaf curl, which is kept in check by keeping rain off leaves. Moisture causes it, not cold, so a fleece cover will not help, but a roof would! Hence the best peaches are on a wall with a veranda above to deflect rain away from their foliage.
In your allotment this is not possible and the only remedy I know is spraying with Bordeaux mixture (copper sulphate mainly) before budburst, on a dry day in February usually, perhaps early March. Then again a month later and even a third time in late April or May. All quite a palaver.
I planted Dobie’s "leaf curl resistant" Avalon Pride three years ago. It is uncovered and unsprayed, gave some peaches last year but looks unhealthy with some leaf curl. Sometimes trees stumble on for a few years with moderate curl and then suddenly die. I hope yours survives!