hello
i've a dd with hemiplegia, right sided.
have you looked at www.hemihelp.org.uk ?
they have loads of printable /download-able info, plus a message board etc., really useful.
if your nursery are a bit difficult and you don't feel listened to, get hemihelp to send the leaflets directly to them, or get the physio or o.t. to tell them, i find that's the only thing that gets through sometimes, far more effective than if it's coming from me!
my dd used pull-ups until she was about 5 ish, longer at night. this was on and off, backwards and forwards, for ages.
also, we used a mixture of normal knickers with pull-ups over the top of them for a while - practising combined with security.
nursery just allowed her to do that and didn't interfere, which i think was the right thing. she wouldn't do anything until she felt ready.
when she got a bit older she told me that it was to do with her balance not feeling quite right or safe, feeling she was going to fall. this resolved when she got tall enough to plant her feet on the floor when on the toilet.
she never, ever used a potty, she just wouldn't, again it was the balance feeling wrong that put her off.
you just have to wait, one day she will be ready.