In my experience, VM won't contact you to tell you about the price increase, it will just happen and once it does, you won't get the additional charge back even if you negotiate a new price.
What I've done in previous years is call Retentions a month before your discounts end - I find the phone App is the easiest way to find exactly when this is - and negotiate then. My Promotions & Discounts end on 14 June 2023, so I will be calling them mid-May.
It's a good idea to get some quotes from alternative suppliers and to be aware what VM are currently offering new customers. Ultimate Volt is now being offered to new customers at £75/m for 18 months (Gig1 Fibre Broadband, 230+ channels with Entertainment, Anytime chatter, Netflix Standard + O2 unlimited sim)
https://www.virginmedia.com/broadband/broadband-and-sim
With Sky likely to be pushing its Now, Stream and Glass services in 2023 you should be able to get a competitive alternative that VM will react to in negotiations.