@WomblingFree & @ASDismynormality - is this the chocolate spread you remember? I remember it fondly from my childhood, though I think the pot had been slightly updated by my time (b 1956). The pot was waxed cardboard, (though I think it later changed to plastic)
While googling for a picture, I came across a forum discussing it, and someone suggested that Waitrose’s ‘seriously chocolatey chocolate spread’ was very similar - I might give it a go...