The ground track from the Virgin site shows the launcher crossing La Palma at around T+ 560s. The vehicle is in the Earth’s shadow but the second stage motor will still be burning at that point (SECO is around T+ 590s). It will be over 500km up when it crosses over LP. It might be visible coming up in your north but I have no idea how bright the exhaust plume would be at that range and you have a bright Moon to contend with as well.
Thanks. I think there is a fair chance here and I have tipped off a few locals with an interest in astronomy, including a pointer to this discussion.
Nothing we can do about the moon but perhaps wide-field binoculars may help; the lack of daylight will definitely help. I’m certainly going to give it a try, weather permitting.