Almost certainly - almost all VM deals are fixed discount, rather than fixed price, so with any deal from last year you would expect a price rise notifications. But the notifications are being staged, so yours may not yet have been sent. And for a few customers it may be lost in the post or via failed email, or contact details may be incorrect. If you're one of the very, very few on a fixed VM price contract then you won't be liable for the increase.
Due to different T&Cs, in response to the O2 increase you probably don't have opportunity to renegotiate or cancel, but in response to any VM notification you will - and if you bought the services as a single bundle (rather than adding Volt benefits by taking out an O2 contract), then I'm pretty sure the VM cancellation rights include the O2 deal under UK consumer rights law. Although if you wanted to do that you might need to get heavy with O2 and maybe even engage Ombudsman Services to force their hand, as the left buttock doesn't know what the right buttock is doing when it comes to VMO2.
If you do cancel, VM will soon be on your case to offer you increasingly heavily discounted deals during your notice period, eventually getting around new customer deal pricing. Just be aware that this time next year you won't have the option of renegotiating, and if you're on a heavily discounted package you'll see up to double the announced price increase.