I've painted windows far worse than this, without a key
The key to success here Daddy Boots is, with all that time on your hands, don't leave it for another 17 years. A light sand and a coat over every now and then just on the bottom bits will serve you well.
Wait a bit. Now hang on a touch. I'm going to have a stab at this.
No mention of lining, so I'll rule that out. No mention of plastering, so that's a no go.
Right then: I'm going to guess that it's silk so, if it were me, I'd fill my spray with hot soapy water (bucket and brush will do)...
O.k.
If you're going to leave the dado rail on no matter what, then you're first suggestion of just papering the middle with the others the same colour would look bad.
So...
As someone else said, paper below with another paper, or paper below with a supaglypta/blown vinyl type then emulson...
There you have it :!:
Grease, need not accumulate over the cooker. It may be heading for the cold spots when you're frying your sausages, wrapped in streaky bacon with a lit fag, sticking out the side of your mouth.
And..
If you get soda crystals, it's cheaper than sugar soap.
http://www.waitrose.com/shop/ProductView-10317-10001-35011-DP+soda+crystals?source=sho_&gclid=CJ6Iw4zwhq4CFQwgfAod1GHZ3w