Thanks for the advice. I will go ahead and book assistance. I spoke to my mum and she suggested saying it was airport protocol for elderly people to have wheelchairs and then there can be no argueing. I am sure they do not realise the distances involved. Even if they did, they would probably think they could do it as they tend to think they are more independent than they are!
Does anyone know if there is a way to the T1 BMI lounge that doesn't involve stairs?