The proper treatment of a foreign-born criminal:
Tattoo the rapist, robber or murderer with a number. Stigmatising? You bet. The choice to commit their crimes was theirs and theirs alone. Then charter a plane for Angola, or Pakistan or Romania etc. As there are thousands of illegals for each country, this scheme can't lose. Round up enough illegals/foreign criminals to fill the craft to capacity, housing those waiting in removal centres until enough numbers are rounded up. Sedate all deportees humanely and transport them to the plane. Employ a few security personnel to keep guard and order during the flight, also one medical employee to ensure safety of deportees. If need be, build a small group of recovery cells at destination airports such as in Karachi, so that the deportee can awake and get their bearings once rousing from their slumber back in their homeland. They are now back home and no longer our problem. If they attempt to reach Britain again - sadly there'll be nothing and no-one to stop them - they can be identified by the tattoo and similarly condemned by a scar in the same place. Deportation again. No appeals, no lawyers, no time-wasting.
This scheme may not necessarily be much cheaper than the proposed one. However my idea does not in any way reward the criminal with liquid assets - this is very important. In the same way that jailing a person for owing fifty pounds costs thousands to imprison them, sometimes important messages need to be sent out to the general public rather than worry about expense.