Hi Bocochoco, and welcome... but what is the reason for adding campden? The Motts will have been made to satisfy food sanitation laws as would the apple concentrate (unless that was made by your next door neighbor - so both of these ingredients are essentially bacteria and yeast free until the moment you open them. The sugar is going to be so dry that no bacteria will survive on it - which is why we don't need to refrigerate sugar and can leave it out in the hottest climate. In short, you need think about the value of sanitizing fresh fruit or freshly pressed juices but not juices processed commercially.
If you are back sweetening and your recipe suggests that you are, then you really want to add BOTH K-meta and K-sorbate to inhibit or kill of remaining yeast. K-sorbate will stop the yeast from reproducing but it does not inhibit those cells from fermenting sugars.
Last point, and this is more a question: you STATE that the bottling gravity WILL BE 1.026 but it will only be that high (or low) if you add enough Mott's juice. How much juice are you suggesting that a novice wine maker might add to hit 1.026 ... and why 1.026? Is there something magical about that number or about that high level of sweetness? Perhaps your wine maker prefers a more dry wine and doesn't understand back sweetening is usually to taste and not to recipe...
See, wine ain't beer and there is no unfermentable sugars in fruit so the wine SHOULD finish below 1.000 . So to bring the gravity back up to a. specific number you need to advise the wine maker how much sugar to add. Brewers can give you a good approximation to a final gravity only because grains contain complex sugars that even after you have extracted the enzymes to break down some of those sugars others remain that the yeast simply cannot ferment (could be 10 points , could be 15 points)... Wine yeast and fruit sugars don't behave in that way...
All that said, an even more simple apple wine might be "open a bottle of any apple juice without chemical preservatives such as sorbates, pour out a cup, pitch the yeast you have to hand and allow the juice to ferment until there is no more sugar for the yeast to eat. Taste, if not sweet enough add sugar to taste and enjoy. Sure that wine will be around 6 or 7% ABV but making it does not get much simpler than that: you don't even need a bung or airlock or even an hydrometer.
