Peter Griffin Solution;
Find a local pikey.. bung him £20 (at least half the price of a new battery) then have him & his mates do you over “pinch” your car keys (WINK, NOD, NUDGE)
Your car found 20 miles away burnt out after having been involved in a series of aggravated burglaries…
claim on insurance… end of battery problem.
Batteries are stored chemical energy the colder it is the worse they perform, if you have being doing a LOT of stop start in v cold weather (all electrics on full belt, high load not a lot of charging) then your battery would have taken a REAL hammering.
Charge it, or jump start it and take your car on a long run see what happens. If however you do a long run at least once a week in your car then the battery may be waving a white flag..
If however you do