Bear in mind English guns tend to have thinner barrels (to reduce gun weight), and you don't mention what the guns proof measurement is and what is remaining of the barrels after all these years, so you will need to talk to Briley as to suitability.
As well, any barrel work of that type will remove the gun from proof, and that will affect value to many potential purchasers. Most purchasers of older English guns follow the adage of "buy the barrels", the rest of the gun being of secondary import in evaluation.