Thanks Splicer, that's great

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I've also found the answer to my People sidebar problem, by doing what I should have done in the 1st place & looking through other people's posts

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The answer is to click on the key symbol in the same toolbar as the People icon, & there you get options to add stuff to the People sidebar (amongst other things).
I'm not having problems with using Flock in Linux, but I did go through Ed's tips about speeding up Flock. If you want to know where to find his tips let me know & I'll hunt for it.
Any other Linux users please get in touch, I'm sure we can all give each other support. I'm currently using Suse but will be upgrading soon.
I usually go by the name ishabluebell or isha_bluebell in various services, as it's easier for people to remember than my full name.
Linux rocks!