Lots of great advice for which I’m very grateful.
Rather than do the obvious and just bin the battery, I’ve invested in a CTEK charger. It’s been a week or more now and the battery is back normal, which only goes to show that a bit of perseverance can pay dividends?
I’m so glad I ignored the advice to renew the battery, which didn’t really help matters.
Hope others can learn from this, and use the right charger for the job to avoid any risk of battery damage.