Many have mentioned that the best remedy for our corrupt illegitimate elite is to simply put them in the underclass where they belong.
FEED ZEM ZE BUGZ
Remigrating all of Britain's foreigners, while necessary, will probably cause something of a labor crunch.
Meanwhile, executing everyone in authority implicated in facilitating the invasion, covering for the rape gangs etc, would (since this is ~everyone in authority) result in millions dead, which the squeamish might find excessive in most cases. But imprisoning all of them is a logistical impossibility.
Therefore, Britain's civil servants, police officers, quangocrats, traitor politicians, journalists, and so on should be reduced to perpetual serfdom within the service industry. They can deliver the food, work in the distribution centers, pick the apples, wipe the bums of the senior citizens, and perform all the rest of the shit work they insist migrants are required to do.
Furthermore, in recognition of their devotion to environmental Net Zero policies and Safety First, they can be barracked in highly energy efficient (poorly heated/no air conditioning) dormitories in which their every move is recorded, while being sustained on a steady diet of plant-based gruel (good for the heart AND the planet!) It goes without saying that, out of an abundance of concern for the comfort and safety of all residents, alcohol, tobacco, narcotics, and sexual contact of any kind will be strictly forbidden on dormitory grounds.
I believe this is a sensible, moderate solution that simultaneously addresses many of Britain's problems.