Feeding the birds is contributing to declines in some of our most threatened bird species, it's a very damaging activity.
Feeding just benefits common species which are already doing well. These then outcompete rarer species for food and nest sites. E.g. willow tits have already disappeared from large areas of the country - one of the causes is blue tits taking over their nest holes.
Putting out food also does nothing to support the insects and other invertebrates which are fundamental to the ecosystem. If you really want to support wildlife in your garden, just improve the habitat. More trees, shrubs, flowers, undergrowth, ponds etc. depending on the space you have available.