Just spent an hour or two on this site - findmypast .
Done a surname only free search then a copy and paste into an excel file and was surprised to find 2 other Dereks had also been born in Birkenhead one older one younger

DEREK Birkenhead 1945
DERICK Birkenhead 1930
DERICK Birkenhead 1957

Only those who worked at Bletchley Park need apply