@Alan It sounds like your dealer has not been honest with you on delivery times. I am due to order in March and will be wanting to order the B200 Premium plus so I thought I would ring the Motability guy I deal with at Mercedes to try and find any info on the B200.
He informs me that the dealeship should have said their had been a restriction placed on the Premium Plus so there would be no cars been built with that package. Also there is no availability for the Driver Assist option at all at the present moment.
The dealership quoted you maybe April, that is probably correct as my guy looked on his online schedule, the nearest month that came up for him was April. Sorry but it doesn’t look like good news. Did you have to pay a large deposit? I am lucky that I have a very honest and caring Motabilty Sales person.
Take care and I hope your mobility doesn’t get any worse.