I think before you consider paying reparations, you need to confirm a few things:
Are they subtracting from the total all the money and effort that Britain used in ending the slave trade?
Are they subtracting all the money and effort made by Britain in maintaining the Commonwealth?
Are the people providing the money for reparations only those that benefited from slavery originally?
Are all other countries, including non-White countries, also paying?
If you cannot answer yes to these questions, it doesn't seem reasonable to even consider reparations.