UK monarch migratory behaviour?

[Idaho Runner]

Hello!

I've recently heard that monarchs have been introduced (whether
accidentally or deliberately, i'm not sure) to the UK.

Is anyone aware of what these butteflies do in response to approach of
fall and winter? Do they attempt to fly in a south-eastern direction
towards Mexico? Do they undergo reproductive diapause and estivate in
clumps until spring?

Any help would be greatly appreciated!

Andrew Davie
Moscow, Idaho