Help! Interview outfit for the very overweight!

[Psychologika]

I need help I have an interview next Wednesday for a job I really want. It would be a promotion and I would be at a senior level (it's NHS).

Unfortunately, I am am very overweight. I'm 36, 5'8" and a size 20. Please help me find something that won't make me look like a lazy frump.

(just realised the date of this thread....hope OP got the job and is happy and well!)