Had a look with the Search Tool (Rae 😄) but didn't find much that didn't veer of at a tangent.
Anyway, hadn't used the bike for 5 weeks as we had builders in and the scaffold blocked access to the workshop so couldn't get the K out... and of course I didn't have the Optimate plugged in.
Managed to recover the battery but I won't fully charge anymore, which in fairness isn't bad, as it looks like the OEM unit.
So suspect a duff cell. Definitely not getting an Li battery so got down to an Exide (who I think make the OEM) and. Motobatt... I'm leaning toward Motobatt as I've had them before and they've been ultra reliable... and they're bright yellow 😊.
Can't imagine there's a lot of difference between the decent brands (Exide, Motobatt, Yuasa)... Any tales of doom and destruction or are such decisions greeted with a shrug and "buy whatever" attitude?