Hello Kal,
From the school of eliminating the simple things first, I would not consider major wallet-affecting issues before first eliminating that the battery is not the cause of your issues. Prior to the stop- start technology, original batteries usually lasted a good 10 years. Now, with so called intelligent charging batteries, stop-start, etc. who knows how long they will last. I would normally have suggested you get your battery's efficiency checked by say Halfords, but I 'm not sure with this modern technology. Probably worth having a word with your local indi first.
Kind regards,
Gareth.