It's not been commercially viable to sell very low cost, niche items, such as electronic components, on the high-street, for a very long time, at least since the 80s. There's no way anyone can make money by having 100s of inventories of something small, like resistors, of over 100 different values, costing less than a penny each, in 100s of locations and make a profit. Think about how many different resistor values are needed, even for the most basic inventory, say E12 values from 1R to 10R and 1M to 10M and E24 values from 10 to 1M, totalling 144 values and the overhead of maintaining a stock in over a hundred stores: it will easily add to to much more than the cost of each part, even if they're sold in multiplies of 100, which Maplin didn't do. Now consider the proportion of the population who are either electronics hobbyists or professionals. There isn't that much of a demand, compared to consumer electronics, which nearly everyone needs. It just isn't economical.

The only way to make money is to have a few central distribution centres and a mail order, whether it be via the Internet or the old system of catalogues. Maplin might have been more successful, if they had kept their stores for consumer electronics, with a few hobbyist items such as some test equipment and Arduinos and kept the component side of business online/mail order only, except for perhaps one or two stores in big cities, with lots of engineering companies. The store fronts could have also acted as platform for the mail order bossiness too.
Unfortunately for Maplin, it's not even economically viable to sell consumer electronics in retail stores any more, due to competition with the Internet. Supermarkets can do it, because they also sell food and traditional electronics stores do it because they sell white goods and act as pick-up points for Amazon click & collect. It's far too late for Maplin to get into any of the aforementioned. At best, they should close their unprofitable stores, focus more on the ones which do make money and work towards building a quality online businesses.