Our main supermarket is a Waitrose, (been there this evening, in fact). Interestingly, they don't have a particularly wide range of own label stuff, but there are a few clear winners.
We actually prefer Waitrose Essential teabags over Tetley and PGTips for taste. They come in boxes of 4x40 foiled packets rather than 240 in a big box so tend to stay fresher longer.
Their own brand breakfast cereals are OK, but we reckon Kellogg's and Weetabix products are much more palatable.
Waitrose Essential baked beans taste pretty much as good as Heinz and in 4-packs have always been very competitively priced.
Their own brand soups are limited in range and aren't as good as the Heinz varieties, but they are considerably cheaper - however I can usually get the Heinz cans on a special offer of some sort in Iceland anyway.
Mind you, for us, it's not just the food brands vs own label conundrum. Price does have to be factored in when bulk shopping at Waitrose, so we now do a targeted shop at Iceland every 3 weeks or so to keep our overall food shopping bills down - biscuits, spaghetti cans, and Clover are three items which are all consistently very much cheaper. We also do have an Aldi and Lidl in town but I'm allergic to German discounters
, and Asda's car park is permanently rammed and policed by Parking Eye about whom there's been numerous complaints
, so I won't shop there either.