"Scandis at nemos, FL200, 300 indicated for straight in 23"
As I say, it is a while since I went to GVA (sadly!) and I'm not sure where Nemos is as we don't go that way. It could be that they can keep a higher rate of descent longer than BA can?
"I've also on several occasions had BA RJs refuse to turn over the Jura until out of FL80"
Again, rusty on 23 SIDS, but there is a restriction (FL70+ at PAS before setting course, from memory?) Maybe this is the problem? Perhaps the RJs could help?