thanks everyone.
Can't use duvet clips/turn duvet round as she goes to bed awake, then chats/reads stories to herself for a while, usually sat on her chair, but quite often stood by the window 9she likes to look out for dh coming home) before she goes to sleep. she would just get out and then not understand to get back in iyswim.
I do put the covers over her before I go to bed, but she wriggles out overnight, and is left freezing.
We use fleece sleepsuits already, but her room is really cold overnight - can't put a heater in there as she'd probably burn herself.
the grobag travel ones have a slit on the back, and a double zip at the front, so no good, but thanks anyway.
I have looked at the fledglings catalogue, and the only sleepsuits they offer are the houdini ones, and made to measure cotton for larger children, but may give thema ring and see what they suggest.
dd1 is ok walking around in a grobag, but she would not be able to get back up onto bed (her bed is quite high, despite not being a cabin bed, and her usual method of entry is to swing one leg up sideways and heave herself on, so can't see it being possible in a grobag...)
I have double suited her the last couple of nights, but it is a faff as she doesn't understand one the first suit is on that she needs to put another one on, so that's why I thought of a grobag with legs.
From research today, most fleece suits are rated at 1-1.5 togs, and she always used to have a 2.5 tog grbag, except in extreme heat, so no wonder she is chilly.