If Partridges are interested these must be worth a bit. It's difficult to find genuine private buyers.The top dealers and top auction houses haven't got the problem. The dealers already have a network of collectors and private buyers to approach. The auction houses, for all their hefty commission, have the same,plus the advantage of targeted advertising, sending catalogues and putting catalogues online, enormous worldwide coverage, internet and phone bidding, specialist sales, and their reputation as 'the place to look'.A lot of the bidders at the best auction houses are private buyers, so you may have private buyers (worldwide,too) fighting over the lot, with extraordinary prices in consequence.That's worth the commission in itself.
Try taking the pictures to a top London house for their free estimate.That's a start. If you like then you can go to various dealers using the estimate as an aid.