The process of setting the divert is the same for UK numbers as it is for roaming or foreign numbers. However, diverting a call to a number that is outside the UK will be classed as an International call and charges apply. https://www.plan.com/pricing

To apply a divert, dial the shortcode **21*phone number#

Dial  ##21# to remove the divert.

To help manage your costs we offer a couple of bolt-ons for International calls and messages. To view and apply the options, from your my.plan dashboard go to:

PRODUCTS > VOICE > INTERNATIONAL > BOLT ON/INTERNATIONAL > [select user] > ADD and choose from the options.

¹account permissions may apply. Contact your account administrator.