OP have you visited www.drinkaware.co.uk. The weekly recommended maximum limit is 14 units (based on average pint of 5% cider) = 6 pints of cider.
Here is some Australian guidance for what might put an average person over the 0.05 Blood Alcohol Content limit (England is 0.08/Scotland is 0.05) adf.org.au/insights/blood-alcohol-levels/
For men of average size to stay under the limit: no more than 2 standard drinks in the first hour and 1 drink per hour after that.
For women of average size to stay under the limit: no more than 1 standard drink per hour.
The web site states clearly that This is only a guide. You might still blow above 0.05% even if you follow this.
If your husband has one pint of 4.5% ABV cider, that is 2.6 units of alcohol.
So really, if you are in the UK, he should not be driving unless he is sure his body has processed the alcohol after even one pint of cider. I have had a friend who was a diabetic and had a stage where he processed alcohol very slowly without knowing it. He was not a big drinker.
Here is some information from Drinkaware:
There is no fool-proof way of drinking and staying under the drink drive limit. The amount of alcohol you would need to drink to be considered over the driving limit varies from person to person.
It depends on:
-Your weight, age, sex and metabolism (the rate your body uses energy)
-The type and amount of alcohol you’re drinking
-What you’ve eaten recently
-Your stress levels at the time
Drinkaware says 'Even small amounts of alcohol can affect your ability to drive so the only safe advice is to avoid any alcohol if you are driving.'
Lots there, but I hope that helps. The Drinkaware site has a calculator that will give you the units (might even be able to do it by brand).
And that is that avoid any alcohol is advice that I follow as an Australian where random breath testing is very very common and the fines and risk of loss of licence is very high. As well as the chance that you could actually harm someone through even being just around the limit. I also know two people crippled by drunk drivers (separate incidents) The line 'if you drink and drive, you are a bloody idiot' and always have a designated driver has been drilled into the population for as long as I can remember.