It almost certainly breaches the Consumer Rights Act. A dealer must not knowingly sell a vehicle which has been illegally modified. The purchaser would find out as soon as they tried to insure it and presumably would wish to exercise their rights and return the vehicle.
In practice I'd imagine that the dealer would offer the car with the original steering wheel (and passenger airbag), leaving it to the customer to decide. Either way it seems like an enormous risk to take even without the obvious safety implications.
Another reason to stick with buying older cars if you want to modify them!
