Boring broadband question

Currently with TalkTalk, but contract (ie initial 18-month discount period has come to an end). They offered a decent package to stay, but can find better elsewhere (with PlusNet in this case). We’re also moving house next week.

If we sign up with PlusNet, do I have to bother cancelling with TalkTalk, or is it automatically switched? It says we’ll have to wait a minimum of 10 days to get installed on PlusNet (for the new address), and we don’t want a service disruption while we’re still in the old place for the next week, so I’m thinking it might be easiest to book PlusNet as a totally new account, then cancel TalkTalk after next week (it needs 30 days notice so another payment period regardless).

Fucking stupid you can’t just do this instantly, it’s 2019.