I'm trying to track down ships lines and a body plan for RFA Engadine (helicopter support ship):

I've tried the NMM, but they don't have any. There are some stored in Scotland, but locked away and out of reach of Joe Public (believe me, I've tried!). Does anyone know where I could find such elsewhere?? At this stage I'd be happy to receive ANY drawings of her!
The only other option is the scale model at the Fleet Air Arm Museum, but I'd need to get inside the class cabinet and muck about with it, plus I'd rather not use another model as a source.

Any hints, tips, suggestions and even drawings gratefully received...!
Many thanks
Andy