Does Windows security offer the same level of protection as Avast Premium? Hoping I can ditch the £59 that Avast costs.
59 quid for Avast
(or for any other malware package like that for that matter) ! - you are being ripped-off BIG TIME

!
PS: I used the free version of Avast for a short time - but got totally fed-up with the continual "buy me" prompting .
I normally pay around £23-25/year for a
10-device licence from Kaspersky (not used now due to their
possibly dubious Russian connection) or Norton 360, and bought as downloads from Amazon to cover 2 phones, 2 tablets and 4-6 PCs
(depends on how many are working at the time!) - so that works out at about £2.50/year, or 5p/week, per device. Also, there's a small amount of on-line storage cloud storage and a VPN included.
As for the relative "efficacy" of those packages versus Windows Defender? Well, that's a "moot question".
Probably a "little better" overall, and almost certainly a lot more configurable in terms of how you can set them up to scan your devices, and with more in-depth analysis of dubious things like "hidden malware" (Norton has found stuff "hidden" in really old files on my NAS &/or USB drives on several occasions when doing system scans - Windows Defender never found those).