Attempts have been made to bring back the Dewhurst name:
https://www.telegraph.co.uk/finance/newsbysector/retailandconsumer/8648298/Brand-Cellar-to-revive-Dewhurst-butchers-brand-in-the-UK.html
As has been pointed out on a recent thread, while BT no longer operates a telegram service, there are several independent companies which do so.
Immediately before coming to this thread I moved my VHS video recorder (which is now used solely for playing all of the hundreds of videotapes I've still got) to a more accessible location in my living room.
I've never thought of Fenwick as a large chain and I certainly can't recall ever having been in any of their stores. Indeed, apart from the one in Colchester, I can't even recall ever seeing a branch of Fenwick. (They've currently only got 9 stores).
Debenhams has been terminally ill for at least a couple of decades, appealing neither to budget shoppers (who'd rather buy their clothes in Primark and their cosmetics from Superdrug) nor to those with money to spend on luxury items.
M&S is rightly positioning itself in the market place primarily as a food store (with increased ranges and home delivery services) and so would seem to have a fairly healthy future (even though many of its fashion-based stores might go).
W H Smith is a chain I certainly wouldn't buy shares in though. Their management can't decide whether they're principally a bookshop (with Waterstones often having better deals and certainly having a better range, a stationers (with many discount stores being far cheaper and Ryman better at offering supplies to business users) or something else. (They've tried toys and games, they've tried CDs and DVDs too, but they've never been able to match the offerings of other High Street retailers). It's only their presence at transport hubs, and their tie-in with the Post Office, that seems to keep them afloat.
I also wouldn't rush to invest in Boots. Supermarkets have largely taken away their pharmacy sales, the likes of Superdrug have stolen away their customers seeking cosmetics and their dabbling in other areas (such as photographic goods and homewares) never seems to got them very far.
There has been a recent thread about vanished names from the past. Without bothering to refer to it though, I can think of Mac Fisheries (and, later, Mac Markets), C & A (although they're still going strong in most other European countries) and International Stores.