Just an FYI: Baja said it all! I live in Phoenix AZ where the temps for the last 15 days have averaged 110º during the day and 92º overnight. It don't water until the temps drop below 85º overnight. What I do is mist the plants at around 6 PM to help lower the temps at least for awhile at night. It does help them at least some and makes me feel better at least! The temps you have described in England at night should not be a problem to water. Just let the soil dry out before watering again.
