According to the O2 website, you can activate through the My O2 app if you're already a customer of both services
https://www.o2.co.uk/virgin-media-o2
This does look to offer more than the Oomph bundles did (which was just the speed boos IIRC?) Though Ultimate Volt at £99pm is more than I saw Untimate Oomph advertised for in quite a while - it seemed to be either £79 or £89 whenever I looked.
The £25pm O2 element of the Ultimate Volt bundle is also subject to an RPI + 3.9% increase every April whereas VM tended to just pluck increases out of thin air, so it could work out berrer or worse for the customer - though with inflation set to rise I suspect its the latter.
This is the bundle page on the VM website
https://www.virginmedia.com/tv