Has anyone run the numbers of how UBI would be financed? For the cost of the current welfare system in the UK we could give every man, woman and child £3000/ye

Has anyone run the numbers of how UBI would be financed? For the cost of the current welfare system in the UK we could give every man, woman and child £3000/year, approx. This assumes that the cost of administration is basically zero, so it would involve sacking all the employees of the DWP or whatever it’s called now. Well, they would be entitled to UBI too... it has to be “universal” and “basic” or the numbers don’t work