Hello Ivor - that is kind of you to say, I wouldn't say I am an expert at all, but I do take a keen interest in some of the cars for sale and there can be quite a variation in prices.
https://forum.triumphdolomite.co.uk/vie ... hp?t=37875
The link above will take you to a similar discussion recently had regarding prices.
However, as you say, condition is everything. Bodywork repairs in particular being very expensive to carry out, especially if entrusting a garage to undertake the work. Mechanical repairs are potentially easier to put right if you are handy with the spanners, however if engine work etc is required by a specialist the costs can add up too.
When you look at cars such as the one you mention on Car & Classic, it clearly is a good example and one would hope would not require too much in the way of mechanical or body repair. To purchase a project and restore to that condition would cost more than the price it is for sale for, so in many respects it represents better value. I would expect it to be A1 for that price.
Original cars that either haven't been restored or ones which have to an excellent standard with sensible upgrades perhaps attract the most attention. A heavily modified car may limit the audience a little.
Dolomites (especially Sprints) have often been undervalued, so it is encouraging to see prices pick up. They are all lovely cars - practical, good looking, great club! and with a good bunch of fellow owners to support.
Depending upon your location Ivor, I am sure a local club member would be happy to look at any potential purchases for a second opinion for you.