I recently got this loco unboxed from Ebay. I am planning to replace the body, but cannot get the existing one off. Advice appreciated!

The under side says "Grafar Ltd Made in Britain", and it looks like it is not a split chassis (I found a video for that model on Youtube). I see four screws, two in the corners under the bunk, one under the chimney, and one between the first and second axles.

Pretty sure it's just the 2 screws at the rear, and the front is held by prongs?  Otherwise it'll be the front screw as well.  Definitely not the middle screws.
Just try loosening the screws and the body should start to come loose too.

If it's the original Graham Farish version it is the front screw which also holds the front coupling in place, undo then lift so body comes away from the bunker end of the chassis.

All but the middle one had to come out, then the front end comes out first. And yes, the front coupling comes out too.

Thanks for the help.