I'm going to miss Maplin, but both tend to be priced for convenience (as in "I've got to have it today). For example, the other week I bought a USB3-Ethernet dongle it was five times the price in Maplin as the first place I looked on-line.
For some stuff, I've found the Argos ordering and delivery experience very good. Always next day delivery, sometimes today, for pick up in store.
Otherwise, there are a number of computer repair shops on the Old Kent Road and Walworth Road that I've found give reasonable service.
I stopped using physical stores to buy computer equipment years ago: online shopping suits me better as it works out cheaper.
I remember when, back in the 90s, I used to trawl Tottenham Court Rd every time I needed some new electronic hardware: going from store to store, getting quotes, then asking if they could beat that quote.
Used to take all day and, even though I was younger and fitter, it was exhausting...