Increased premiums for in stock items when stock is scarce is not unreasonable IMO however it depends how much. In any case I understand that this is easily determined by what the buyers are comfortable to pay, the competition will be doing the same and the buyers will side with the better price in that particular local market, ofcourse customer service and ease of business make a difference. I happily pay $1 or more extra per oz to get better service, less wait time with a dealer v's one with poor record of customer service. (when you have to enquire if they can update an invoice paid after 2 weeks etc)
The secondary market in Silver has been almost non existent anywhere for the last year or duration of Covid. However some US dealers are paying over spot to get secondary into their inventory.
I think it's boom time for all G&S dealers, the ones I've used in Au seem to have done exceptionally well over the last 10+ years no matter what the market was doing, some have done well with cryptos too even if they have the highest premiums anywhere.
The market is short of product, and I hear rumor that mines and even dealers are holding stock back, which is good and bad I guess, bad if you are buying good if your bought and holding.
I've been lucky to get some Eagles of older years at a very good price s/h last week. Dealers selling new eagles $16 ea more than I paid. (Probably 10 pounds in your money)