In theory you may be correct Paul but in practice it could be difficult to establish a fair valuation that an insurance company would accept and if they were to appoint their own appraiser then the consequential premiums are likely to be unaffordable as some people have discovered. I suspect the best you could hope for in practice, assuming you have really well documented your model, and it is included under your household policy, would be something based around the going Ebay rate for a broadly comparable item.
It will however be interesting to see if anyone has direct experience.
It may be easier to get a payout if your model was in a show and covered by the organiser's third party insurance but that also raises interesting questions. Over many years as MEX judge I used to see some quite fantastical estimates of value offered up by entrants – £10,000 for a kit in one instance as I recall and I remember thinking '''good luck with that if it falls off the stand!'
Colin