The U.K will get a tsunami. But only a couple meters high. Nothing like the Americas will face. London will be sunk along with any other western/southern coastal U.K town. But again wouldn't be very large and wouldn't go that far inland in U.K.for once, I’m glad I live in the UK…christ
If this tsunami was rated as a tornado for destruction rating U.K would get a F1-F3. But Americas would get a F5-F8. For easy comparison of strength and I know it doesn't go to F8 just is analogy meaning beyond comparable scale of anything we know.
There will likly be little to no warning for Spain & U.K as wouldn't take long for the landslide tsunami to clip you guys.
In fact reports of a tsunami in EU & Africa will likly be Americas first warning sign besides half the mountain sliding into the ocean.
If after half the island splits there might not be any infrastructure left working on the island to report it so a tsunami in EU/Africa could be our first warning.