Probably during the same cold spell, my 23-month-old lead acid battery was OK turning the engine over, but no luck starting - this happened twice, in spite of taking the battery out & bench-charging and cleaning the posts and applying a good coat of petroleum jelly to the posts and terminals in between, just to make sure.
When I bought my 1997 +4 a little over 18mths ago, I decided to keep an automatic battery conditioner connected 24/7, as I didn’t fancy being caught short if there was a good “Morganeering” day........
I knew that the battery had been replaced some 6 weeks before I bought my car, so, hoping to get a replacement if it had a 2-year warranty (🤔), I contacted BHM who had supplied it, and, long story short, after getting advice from their helpful team, I ended up topping up the cells with de-ionised water and adding 2 battery reconditioning tablets to each cell, & no problems since.
The tablets are Granville ‘BAT-AID” tablets (available at most ‘popular’ motoring stores and from online web stores at about £4 for 12 tablets) and, for me, worked a treat.
Hope that helps 🤗.