Parasitic battery drainage or just lack of use? Aygo 2010

Hi, I've had my 2010 Aygo since 2013 without any major problems. I had a flat Battery in October so replaced with a Yuasa HSB202 Silver 12V Battery.

Since then the new Battery keeps going flat, which I totally understand could just be due to the cold weather and the fact I sometimes only drive it once a week + shortish journeys + it's getting on in age now. But it has been on quite a few longer trips lately and it's been fine every other year until now, so I wanted to check if anyone had any thoughts on if it's just the lack of driving, or if it could be a parasitic drain, from something like the bluetooth?

I spotted this thread here. I don't use the bluetooth but it does seem to sometimes switch off completely, sometimes blink. I could attempt to disconnect it as per the thread? The display on the CD player and light on the AC unit have also recently been intermittent (pushing the unit in seems to solve this - I've read that a dodgy connection here is a known fault with Aygos?)... I'm not sure if any of this is related.

Halfords checked the Battery and said it was fine, up to 80% charged after a jump start from a Battery booster and a 20 minute drive, and that the alternator & start up motor were fine too. They said they could put a larger battery in, a 640A rather than the 440A. Would this be worth trying? Toyota say they can do a trickle charge & check on the battery but not sure if this would help?

So I wanted to ask if I should just expect the battery to keep dying after 6-7 days without use, or if the above issue or any other faults are worth looking into please? I WFH so it would be tricky to try to get more mileage in just to keep the battery topped up, but do understand if that's the only fix.

I don't know too much about cars so any thoughts/advice would be greatly appreciated. Thanks!