The DfT proposal is a very poor piece of "research". Their cost estimates (of forcing every N back to G) are done along the lines of ... the cost of keeping a car is the cost of annual road tax, or the cost of keeping a dog is the cost of a dog licence. The person who wrote it didn't know much about aircraft.
The min cost of going back to G is about £5k, and that is probably with the easiest case.
More to the point, forcing N to G will strip the pilot of his European IFR privileges, the renewal of which for Europe (the full JAA IR) will cost say £10k and 1-2 years of study. This is a very poor safety argument!