What is the 'orangey' colour on this pine and how do I remove it?
Actually, 'Pumpkin pine' IS (or can be) a natural, aged color of pine.

Painting is the easiest recourse.

Formby's or similar 'refinisher' will strip wood (of varnishes) and leave some patina, after which, a wood bleach (an oxalic acid based, like Savogran wood bleach) would be called for.  

Then, sand and coat with a u/v blocking clear finish.

Repeat in 20 years.

OR

Tell every one its an antique and mustn't be tampered with.  Its the best TLC this beauty deserves.  

Essay on Pumpkin Pine by Richard Mcintosh