Not so isolated
I'm hosted with Memset who have a DC in Reading. Based on the similarity with Names/Simply, I'm guessing they are colocated in the same DC.
If that's the case I find it hard to believe it was an "isolated" incident to a "small number" of Simply's customers.
Memset's status page is quite informative:
"An area of Reading experienced a power failure earlier this morning which affected both the primary and secondary power feeds to the data centre. Issues transitioning onto generator power resulted in power loss to our entire estate. Currently all power has been restored to the data centre and we are working to resolve any outstanding secondary issues affecting a small number of customers.
We will issue a full report once our internal investigation is complete."