You Do Need power plug adapter while traveling from Great Britain to Canary Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Canary Islands are C, E and F and in Great Britain is G. This is how they look like.

Great Britain

In Great Britain, outlets of type G are in use.

Type G

Canary Islands

In Canary Islands, outlets of type C, E and F are in use.

Type C

Type E

Type F