You Do Need power plug adapter while traveling from Seychelles to Channel Islands (Guernsey & Jersey).

Here is Why You Need An Adapter

The outlet and plug type used in Channel Islands (Guernsey & Jersey) are C and G and in Seychelles is G. This is how they look like.

In Seychelles, outlets of type G are in use.

Type G

In Channel Islands (Guernsey & Jersey), outlets of type C and G are in use.

Type C

Type G

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