This is becoming an obsession!
https://www.theanswerbank.co.uk/search/?q1=jennyjoan+quality+street
;-)
Roses and Quality Street tend to be seasonal items in supermarkets, often available only around Christmas (and possibly Valentine's Day and Easter as well). Even then, while it can be fairly easy to find the smaller plastic tubs, the big tins aren't always stocked.
Trolley.co.uk (which tries to keep track of stock and prices across all supermarkets) isn't showing Quality Street tubs available except the Co-op at the moment, where they're available in the plastic tubs. The same applies to the regular stock of Roses.
However the site is showing that Sainsbury's are selling Jubilee tins of Roses (albeit in a fairly small size when compared to the big tins that are sold at Christmastime):
https://www.trolley.co.uk/product/cadburys-roses-jubilee-tin/NZQ184