We have dealt with the estates of 4 sets of relatives and have never listed and valued every individual item.
We do dabble at the bottom end of the antique market and go to auctions regularly, but we just highlighted and photographed, any item that could possibly have a value ( a wedgewood dinner service for example, which theoretically should be of significant value but isn't because they are out of fashion.) We checked ebay for valuations of similar items and printed them out, then did estimates for the theoretical value of everything else. £500 for all the contents of a kitchen, which was a gross overestimate bcause everything went to the tip or a chairty shop.
Providing you put in a figure looks reasonable, there will not be any queries. I think we put a figure like £5,000 as the value of the contents of my parents large 2 bedroomed bungalow. It was a gross over estimate , but £5,000 one way or another, was not going to make much difference to the amount of inheritance tax we paid.