I`ve never used the Pets At Home brand foods but one thing I would do is look at the ingredients and the typical analysis on the bag or online. Your looking for a mix that has good variety and not too many pellets or extruded biscuits. Some mixes will say they are `complete` foods, but they won`t be if the hamster doesn`t enjoy it.
I would recommend Burgess Supahamster, but it depends whether you can get it where you live. Science Selective is actually a complete food, so initially doesn`t require adding to, but hamsters get bored with pelleted/biscuit type mixes, so what I do is use Burgess Supahamster, JR Farm dwarf mix from Zooplus and I add a science selective biscuit every few days as a biscuit treat.
My Russian hybrid loves this variety. x