Re: Weight of a Guitar
Not sure about ParcelForce, but usually the weight doesn't really have that huge of an impact on price. The dimensions are most important, because the limiting factor of how much they can load onto a truck is almost always volume, not weight. If they have an estimator, just see how big of an estimate of overestimating the price is.
It is a little hard to say with out knowing what kind of case it is, cases can weight vastly different amounts. One of my cases when empty feels like it weighs more by itself than my other cases with the guitars in them.