The small blue-bloomed fruits could be mistaken for sloes, which are horribly astringent in the mouth, but these are sweet and delicious. They are probably some form of Prunus domestica, perhaps bullaces, which some old books say occur in the Midlands. Like sloe (blackthorn, Prunus spinosa) they spread by suckers forming a thicket though it's possible that new growth gets trampled by people reaching in for the fruit from late summer. For a closer look see SP2965 : Wild plums, Warwick.
The elephant and castle is the original name for this pub and goes back at least as far as 1880 when it was a humble beerhouse. The name of Simple Simon was coined in the 1970s and was linked to the Shires pie factory that was close by. The Elephant and Castle most likely refers to the coat of arms of the City of Coventry