I'm glad you asked that question. Not because I know the answer but because I had it as a 1986 film and will now have to change a lot of lists! I hope I don't have a lot of those mistakes. I notice that this changed to 1985 with the mention of a Royal Command Performance screening. I'll go with 1985 too.
To answer your question it may just be Helena Bonham Carter. Maggie Smith was considered a lead by BAFTA but supporting by the Golden Globes. I had her in supporting. Julian Sands? Not sure.
It was Maggie I was most concerned with, as I know she was nominated in differing categories. I'm going with supporting.