It was MK plugs for CB and Olive and then Crabtree for Series 5 ( I think)
Last year - and for wont of something better to do during lockdown - I sourced a variety of cheap mains cables to see if they made any difference. These are all sealed units, which would normally be discounted by us audio types...
Merlin Huntsman @ £15 a pop - big 1.5mm wires and quality connectors in the IEC
Stagg IEC cable (sold for £5 for guitar amps) has 1mm wires, good IEC connections and removable plug, so ripe for an upgrade.
Pencon Laptop cables (3 for £5 via eBay) - UK made, 1mm wires. Very well finished for a 'kettle lead'.
Standard Naim Crabtree cable - judging by S/H prices comfortably the most expensive @ £20-30 each
Merlin and Stagg both delivered a more forceful sound, but I felt this came at the expense of musicality and swing. The Naim was good on both counts, or maybe that is just what I was used to hearing. I have a soft spot for the Pencons - very well made and sound v similar to the Naim cable.
main advantage of any of the above is the IEC fits tight into the power socket, which is not something all audiophile cables manage to achieve.