You don’t need to recode/register the battery, nor do you need an expensive stop-start AGM battery.
A Bosch, Exide, or Varta of the right type (096) will do fine, and ensure they have similar performance to the OE battery (around 70+ah, 700+CCA). The variations (e.g. S3, S4, S5, Excel, Premium, Blue, Silver, etc.) are usually just a bit more power and longer warranty.
You can get a Bosch S4 at EuroCarParts for £99 with their latest TOUR60 discount code, or the S5 for £132. The Exide are cheaper and the Varta in the middle.