Oh so it does give 525mm focal length, that's exactly what I wanted to hear!
I mean it's not 600mm but it's only 75mm shorter which I expect will be long enough for most birds in flight, distant animals or subjects I might shoot.
Just watched the video posted above for that lens, it looks great. Nice and compact. Weighs only 625g and about the same size as my Tamron 70-300 which weighs 850g with the lens hood.
I went to pcworld today and got to try out a couple of Sony cameras. They only had the 6400 and A7ii but they gave me an idea of what the a6600 and a7iii would feel like. I was surprised how small the A7ii is, smaller than my Canon 5D mk2 and really not that much bigger than the 6400. I expect the a7iii would be the same size. The buttons are smaller than I'd like and the main wheel on the 6400 is quite flat and not as nice to use as the Canon wheels. Even on the a7ii I didn't think it was much better. But they're not dealbreakers. I got to try out the 6400 and I asked a woman standing near me if she'd mind me testing the eye AF. It really does work amazingly well, the little box stayed on her eye when I asked if she would be so kind as to move left and right which she happily did.
Very impressed.
So I'm going to order the a6600 + 70-350mm. £1039 + £669 = £1708. I'll look into that L bracket you mentioned,
Regarding the wide angled lens, that 16-55 f2.8 is expensive at £839! The 10-18 f4 that you and Stephen recommended is £509, a bit more palatable.
Now I'm not sure what to do. After spending £1708, I don't really want to spend another £1348 on two more lenses. Do you think I can get a couple of good and less expensive 3rd party wide angled lens? I'd buy a Sigma MC-11 adapter. It would have been easier choosing for a full frame camera. A 16-35mm would have given me the wide angle I needed up to 35mm. And then I already have my 50mm f1.8 canon lens. But in this situation with the aps-c, I'd need the 10-18 for wide angles but I'd have to also buy another lens like the 16-55mm to get me something equivalent to 35, 40, 50mm, etc. Or do you think maybe a 10-18mm would cover most situations without needing to buy another lens, at least, for now?