Wow, thanks for all of this! Loads to work on!
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Also scales in octaves on 1 string (particularly G string). Painful to start, great for flexibility. You could try some 3 octave chromatics for intonation.
That's a really good idea, although I will be very careful of course as my viola is quite large!
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Vibrato...try to play for a day without any vibrato at all. None whatsoever. Then the next day, do 5 minutes no vibrato, and then play "normally". It makes it so much easier, you might think your vibrato isn't sounding properly but this exercise tends to show that it is.
Oh, I noticed that I have a tendency to over-use vibrato, which is affecting my intonation - at the orchestral course I've just been to, I kept getting pulled up for my intonation

We were playing some pieces that didn't need vibrato and it was so hard not to use it! That exercise also sounds really good, I need more control over my vibrato (I THINK I use finger vibrato).
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Bowing...oh I love this one, best thing to do is video yourself.
I don't actually have any means of videoing myself

but I'll practise in front of a mirror. I know that my bowing is improving but I still need extra flexibility.
Thanks for all these exercises everyone, I've got loads of things to keep me busy now!