Nappies for chunky baby/toddler?

Hi everyone, I’m from the UK but live in Malaysia, where my son was born. We’re heading back to UK at the end of this month to visit and I’m starting to think about the practicalities! He is now wearing size XXL here which is 15kg+. He weighs close to 13kg but the XL don’t fit well anymore, he’s always been big around the tummy! We tried a few different brands before settling on one - Merries, a Japanese brand - so hoping to find a good one on first try back in UK. From brief research, it looks like supermarkets do their own (not a thing here) and there is also Pampers. Any suggestions?