It's a shame as I have fond memories of "Marks and Sparks" as my nan was a loyal customer back when I was a kid, so we had many visits to the one in town.
Sadly in recent years it seems to have declined markedly - my suit came from M&S IIRC and is alright for what it is, but new stuff seems uninspiring. Also the food and clothes business model seems like a bit of an odd / unique one too and with such available choice maybe people are less concerned now about sourcing these from the same place / being loyal to one shop.
Of course, as with most bricks and mortar retail outlets the enormous elephant in the room is the internet, while I think in terms of clothes M&S stuff seems dated, frumpy and of zero appeal to all the markets (sadly) being served by cheap fast fashion. The food outlets probably aren't big enough to be competitive with supermarkets, while for most (those who must drive everywhere) utility town centre shopping has been killed by traffic, traffic restrictions, a lack of parking and a lack of decent alterntive transport.. urban centres expanding and most living / shopping on the outskirts.
My grandparents never had a car so walked or bussed into and out of the town centre to buy food; now I'd wager those who live in their old place would simply drive to the local Sainsburys, which is probably a similar distance but a lot easier to access by car.
Sad time really..