I'm a tad sceptical that the conversion from DAB to DAB+ is to blame, as I checked when Planet Rock moved and it was October 2023. They posted on X on that date "Planet Rock's digital radio transmission has just been switched from DAB to DAB+".
That being said, I just found this - https://www.digitalradiochoice.com/news/absolute-radio-kiss-kisstory-and-magic-radio-to-switch-to-dab/. I don't know what others listen to but this happened on 31st March 2025 - the article says it covers just Absolute Radio, KISS, KISSTORY and Magic Radio.
I just did a quick check - Bauer Media Audio UK is a UK-based radio division of Bauer Media Group owning brands; Absolute Radio, Greatest Hits Radio, Jazz FM, Hits Radio, KISS, Planet Rock, Magic, Kerrang! Radio and Heat Radio.