Burco not switching off properly

[lord groan]

Has anyone noticed that their burco remains on when the simmerstat is set to 'off'. I noticed this on a friends burco, he had just bought it 2nd hand, we were testing it and it heated up fine, if the control was on max the element stayed on, if it was between 1 and max it cycled on and off as it should, when we were happy that it all worked fine we switched the rotary control to OFF and the boiler switched off! I noticed after a couple of minutes that it suddenly fired up for about 5 seconds and then went off again. This kept happening every couple of minutes.
We dismissed it as a dodgy stat and decided to switch on and off at the wall.

Today I picked up another burco, again 2nd hand, and after testing the electrics with a meter I put enough water in to cover the element and fired it up. Exactly the same result as above, everything works 100%, except when the rotary control is set to 'off' it comes on for about 5 secs every couple of minutes.

These are both older boilers without thermal fuses or thermal protection thingummys on the underside of the element.

Multiple choice question: Is this -
A. A well known fault?
B. A design feature working as it should?
C. Thats just how it is?
D. The boiler faeries hate me?
E. Something else.

Any polite suggestions gratefully received

[Fil]

D.. ?

???

my experience is limited to my old burco which is as simple as they get copper plate elements bolted to the pot bottom underside. off, low,,med, and hi are the dial options and off is off