According to my pottery marks reference books, the PK in a seal type mark is for Philip Knight of Lancing, West Sussex. The entry in miller's pottery and porcelain marks (Gordon Lang) states, " Studio-type wares, animals and portrait busts were produced from 1950 ... impressed seal-type mark with initials in relief was used from 1962."
That does rather seem to match yours... but I have not been able to find any other examples of his work online to be able to compare for you... I'll ask some folks who may be able to help and come back to you.