If you can't find the kettles at Tesco, Woolworths have these for a fiver each. The elements are identical.
That's four elements for the price of one from H&G ... keep your inner Yorkshireman happy!
By the way -- this confused me at first -- there are two cut-outs in these kettles, both metal disks. The first is beneath the switch and flips it off when the kettle boils. The second is inside the round bit itself, behind the element, and is a 'Oh my God it's going to melt!' sort of thing. This can be kept unless it cuts out during the boil.
I'm working on ways to shroud the plug.
Thanks for the photo tutorial, Des -- very handy.