The first chocolate eggs may have been introduced in England by Fry's in 1873 or by Cadbury in 1875.

The Tatler - Wednesday 21 March 1923
As there is a commonplace concern that the Eggs are sold at the wrong time of year, the most remote sale from Easter-time we can find is a report from 'The Derby Daily Telegraph' of Wednesday 13 December 1950 that Easter Eggs were on sale in Derby Market.