Lead-acid batteries hate winter, and they also hate inactivity. So if you're planning on leaving the battery on the bike for three months in sub-zero temperatures, you might as well save the fuss and put it straight in the bin in October.
If you've got an Optimate trickle-charger or similar, it may be convenient to leave a plug permanently wired-up to the battery terminals. Route it to an easily-accessed location, such as under the pillion seat, as shown, and you'll be able to plug in the charger when needed without even exposing the battery.
If it's kept charged, it'll be okay down to normal UK winter low temperatures.
Lithium batteries are more forgiving, and cope better with lack of use. But they also cost a fortune, so best not take any chances, and keep yours on charge with a proper lithium charger.