Is it a forum member or a known truck? It looks like an ok Cruiser and the seller seems honest and open. An opinion on its condition can only be validated after a good inspection and even then its subjective as its the inspectors opinion. It has things on its side, colour, model, bit of provenance, mileage, tyres, work done etc, against it is a lot of interest,maybe even from forum members who are keeping quiet and watching how things unfold. Theres one thing for sure, it wont be like new underneath after 16 winters.
In my opinion it will make £5900 at a guess.
Andy