BR, you mentioned buying insect mix.
last year I made up a batch of my own and have been putting it out this winter. I had wasp traps out (jam jar with apple juice & jam in most of the year) and along with the wasps trapped loads of flies too. So strained off the mix, picked out the wasps and mixed the rest in with a wild bird seed mix some meal worms (dried) and a handfull of maggots (from fishing tackle shop) and suet, some mixed fruit bits, chopped nuts, currents etc. Put it in yogurt pots or tubs let it set, pop in the freezer ready for the cold weather. Before putting it out I let them thaw out a day or two and then hang them on the bird feeder or trees in the garden. The birds go mental for them. They are usually gone the same day, aposed to the bought stuff that lasts a few days.
we hade Blue,Coal, Great & Long Tail Tits going at them, Robins, even the Gold Finches ventured off the niger seed to have a peck at them. The Black Birds frighten off the Starlings to get at them and even A thrush has been going at them too.
The only downside was we lost a Blackbird who was so intent on feeding it did not see the Sparrow Hawk that visits us occassionaly.
And NO I am not out in the sticks, just a suburban area near fields. We are very fortunate and get a lot of birds in the garden, but we have been encouraging them a lot.