Value is always dependant on the coins condition. Though for the Holmes 50p they only minted 210000.i think decent ones sell for £150. The brexit one was minted by the millions the first go round. Not sure if they'll make all that many this year.
I am ot sure where Gincoin43 got the mintage figures as they have not been released yet for 2019 and 2020 coins.
My experience is that Sherlock is very common - you can see them on Ebay at rock bottom prices (£0.50 upwards). They may get more collectable, but I think unlikely to worth much in the foreseeable future.
Brexit coins - they announced an initial run of 3M with a follow issue of 7M planned. I suspect the second run may not happen now as the demand for cash has slumped thanks to Covid. As a result, this one may go up a bit.
The recent coins that have jumped in value are the 3 scarcer 2018 Beatrix 50ps - Flopsy Bunny, Mrs Tiggiwinkle and Peter Rabbit with the Radishes. These can make £5 to £10 each - they were more before Covid, but I think people's attention is elsewhere at the moment.
Ah - that article was written in May 2019 as the Sherlock 50p was just being released and was just intended to get people interested in them. The 210000 figure relates to the Kew Gardens 50p, which is scarce and does make £150+. BUT beware of both fakes and later restrikes of the Kew Gardens, which go for much less.