Different processes in Scotland, and England and Wales.
The Scottish legislation is further on. The Scottish Govt had blurred sex and gender ID but that's come out of the bill. But there'll be two new voluntary questions on sexual orientation and gender ID. Parliamentary committee said sex question must be binary (M/F) as the plan just now is a three-way answer.
English legislation has just been introduced, I think. Same new voluntary questions but the census authority has already said it's sticking with a binary sex question. So a better starting point.
I think the parliaments consider the draft census questions later this year (so still not out of the woods in Scotland with the drafting of the sex question AFAIK).