I'm sure that if maplin were competitive on price with online retailers that they would still be around now.
That's true, but not terribly helpful. If they were an on-line only retailer they'd have the same relatively low cost base of other online retailers, but then they wouldn't be a bricks and mortar retailer with a wide geographic footprint. And for on-line only we've already got people like Farnell and RS, a range of smaller specialists, not to mention Amazon skimming the non-specialist market, aided and abetted by that company's devious tax avoidance.
There's no way for a high street retailer to compete with online sales, because of business rates, sales staff costs & the support overheads, property lease costs, and the low turnover per square foot of a retail outlet. My local Maplin has/had a business rates bill of about £50,000 a year for a large retail park unit. Staff costs I'd guess at 4 FTE, so fully loaded for corporate costs that's £120,000, lease costs I'd guess at £200,000 a year for this location, plus utilities, insurance, maintenance, etc that I'll guess at £30k, giving me a neat round £400k a year for one retail park store. That's £400k extra that Farnell or RS don't have to factor in. It's over a thousand quid a day in this store that on average probably only sells about a thousand quid of product a day....