People sell posessions all the time whether on EBay or elsewhere so that shouldn't be an issue.
The key thing is clearly the 'hobby seller' tag although why that should invalidate your home insurance I have no idea. Surely any 'hobby' items regularly put up for sale could be excluded from cover.
This sort of grey area does crop up elsewhere. Like Bob I write stuff that gets published but that is classed as 'home office' and doesn't affect my cover. My motor insurance does include business use at a small extra premium as I am registered as self employed in regard to work for the magazine. and I can attend events to cover them. It doesn't cover commuting or activities which require constant driving such as if I was a self employed plumber etc.
I think that where you are getting caught Bob is that in making model ships you are being classed as 'manufacturing' even if you have no heavy machinery(!) whereas 'home office' just entails sitting in front of the computer you are already using for other things. It is all very arcane though which is why a good broker may be able to help by cutting through the tick box mentality.
As another example, we have had problems getting contents insurance (house is insured separately through Housing Association) because we have a low pitch felt covered roof which is technically classed as flat by insurers. The roof was originally clad in copper which developed persistent leaks and the obvious replacement was high spec felt. Leaky copper was fine but modern felt not so good although technically better. but that's the insurance industry for you, rapacious and inconsistent.
Colin