Search for “jelly” moulds on eBay.co.uk, the British site.
Also check out Ruby Lane and TIAS.com. Neither are auction sites, but both are used by professional antique dealers..
Don’t expect to get the catalogue value for your moulds on eBay. You might hit a couple of fevered bidders, but eBay is a low end market for most things. Especially for new and occasional sellers.
If you ask a dealer for a value, tell him you need it for estate settlement. There are three basic values for collectibles.
First is cash value. The dealer offers you a price that allows him to make a profit when the item sells. Which can be months or years from now. The offer will be oral.
Second is insurance value. This is a writted appraisal that can be used by the insurance company if the item is lost to crime or disaster. It is the replacement cost and will be higher than the other two values.
Estate value is the amount you would probably get in a public auction. It allows families to calculate the amount each heir will get , or balance the value of the “stuff” they take home. John gets the Doulton figurines, Mary gets the coin collection, Peter gets the snowblower…etc. This is also a written appraisal.
Expect to pay for a written appraisal. You are getting expert advice and this is how experts make a living.
