Change your supermarket! Princes canned mackerel fillets are £1.40 in Tesco
https://www.tesco.com/groceries/en-GB/products/254864066
but their own brand are only 80p
https://www.tesco.com/groceries/en-GB/products/258574702
(I pay £1.09 for 4 cans of own-brand baked beans in Morrisons).
That doesn't mean that I've not noticed plenty of price rises though. Some of them creep in (in part, at least) through the withdrawal of multi-buy offers. For example, not long ago Morrison's 'The Best' yogurts were priced at 60p each but with a perpetual '4 for £2' offer on them. They're now 79p each, meaning that the shelf price has risen by 32%. However, as there's no longer any multi-buy offer, the
real price of 4 yogurts has risen by 58%.
It's much the same with other products that used to have multi-buy deals, such as chilled ready meals. The shelf price increase has been kept relatively low but, because the multi-buy deals have gone, the actual price increase is far greater.
While I'm far from well off (with an income of around £15k p.a.), I'm fortunately in the position whereby cutting out a few treats (such as eating in Morrison's café a couple of times a week) has allowed me to continue doing my grocery shopping without worrying too much about the costs. However I can well understand why others are struggling.