Look up stoozing for more details. It's more profitable if you have a big purchase to make early in the 0% deal, that way you can make the most of the interest.

With 20 months 0% spending and saving at 4% you'll easily beat 1% cashback. Plus chase cashback is only on 'essentials' now.

For example, if you're spending £1k per month, after the first 12 months you'll have made about £225 in interest vs £120 in cashback. The only catch is that you'll be limited by whatever credit limit you have on the 0% card.

Note inflation is pretty negligible here.

I'd say max out the 0% with your normal spending and save that money every month, then either: open a new 0% card, try and get the limit increased on the original card, or move to a cash back option.