The dissassembly procedure for the mainsprings on the Macnaughton is different from the Dickson/DMB. Doing this by-the-book you should be using a specialist horse-shoe spring clamp (you have to make this yourself) to remove Macnaughton springs. This clamp increase the tension in the bow enough to lift the claw on the limb end out of the triggerplate. Do not be fooled into thinking you can use a combo of pliers and vise-grips, you will just end up cracking it.
The Dickson roller-cam bow mainsprings are under very little tension in the fired position and so have tabs on the limb end to lift them out of the triggerplate without a clamp.
BUT...as my learned UK friends above state, best left alone. These bow springs do not like being tampered with (especially after 130 years) and the last thing you want is to crack one, they are about Ł250 a piece to get a new one made properly.