Thanks for those links. They look perfect, particularly as they move and throw the squirrel off balance. Not cheap to buy mind, but a good investment.
At the moment I've seen no activity. Food sock is still full and I saw a couple of blackbirds come into the garden this morning and then fly over the bird table, ignoring it and over the fence to somewhere else, lol. A robin (or might have been a sparrow) entered the garden too but was looking for food on the ground. But I read that robins and some other birds generally prefer ground feeding.
But I've not put the niger, peanut and suet ball feeders out yet, the only one hanging at the moment is general cheap bird seed. I also read that birds are quite fussy and only like high quality seed so I'll l replace it if it stays full.