Good luck! The biggest auctioneers for antiques and jewellery in Lancs are Capes, Dunn in Manchester. You can bid online through the auction house or through thesaleroom . com. Their site lets you listen to the auction in progress; it's almost like being there. Don't know what your budget is, but even Bonham's and Christie's, in London, have jewellery lots for a few hundred pounds in their regular sales, also online; of course, those houses sell items for hundreds of thousands or in millions too, but those sales are marked out as special. Their bread and butter is in much less valuable lots.
With those houses, you can buy blind. If the room thinks the item is worth even twice the estimate you are probably still safe, but it is better to stick to top estimate and no more than 50 per cent above. They will provide you, online, with a condition report so you can see what is right and wrong with the piece. Local auctioneers often provide the same service online or in person.