Squirrels are a rarity here, period.
The last time I saw a red squirrel was eight years ago in Norfolk.
Grey squirrels are, as Dave Holford rightly pointed out, aggressive, vicious, highly territorial and will happily kill our indigenous and much more beautiful red squirrels in order to invade their territory.
Basically, they are vermin....rats with pretty tails, and I would infinitely prefer to have red squirrels in our town.
But we don`t, and I am content to admire a part of God`s creation for its own beauty, whilst lamenting the effect it may have on our environment.
Rather like admiring a tiger whilst simultaneously worrying about the number of smaller mammals it kills , or a great white shark whilst deploring the fact it may be killing surfers :-)
Nevertheless, squirrel photos from your gardens will be received with pleasure !