You Do Need power plug adapter while traveling from England to San Marino.

Here is Why You Need An Adapter

The outlet and plug type used in San Marino are C, F and L and in England is G. This is how they look like.

England

In England, outlets of type G are in use.

Type G

San Marino

In San Marino, outlets of type C, F and L are in use.

Type C

Type F

Type L