Believe it or not it's actually safer if the road's wide enough. It forces car drivers to slow down and overtake cyclist properly rather than speed past with millimetres to spare. A single line of 20/30 cyclists creates a longer obstacle so it's six of one half dozen of the other, but two abreast is definitely safer for the cyclist even if it is less convenient for impatient drivers.
A good metre out from the side of the road is the way to go and I'm pretty sure that's what recommended by the CTC et al.
As for bunch riding that should only happens during races on the open road, which is very tightly controlled, with lead and rear cars with riders being penalised for going over the white line.
With regards to bunch riding I'm not sure what you expect road racers in the UK to do stop racing? By that logic there shouldn't be any road runners racing on roads either, something which causes far more disruption.