Yes, that is correct. The levers ARE on the port side but there are 2 sets of levers, one for each engine, 4 levers in all.. unless I've misunderstood what it is you're querying
You have to have all 4 levers forward otherwise you'll only get s/c to one engine and that would give you the uncontrollable yaw you mention 
EDIT:
Craig.. I've looked again at those levers AND looked at the PN's too. As you will already know, the outboard pair are air intakes and move independantly and the inboard pair are the s/c controls. There IS a tendancy for the Beaufighter to yaw on takeoff and the PN's advise getting the tail up as quickly as possible to lessen the effect. However, I've not been able to replicate the s/c only giving boost to one engine. The engines don't run exactly syncronised (initially) but they do settle down when running to give the same readings from any given throttle opening.
In my defence, I couldn't really beta this model as the pc I had at the time wasn't powerful enough to run it. The ground would go to that nasty opaque green goo and the model fragmented
Hopefully, DG will pop in and offer some worthwhile words of wisdom in the not too distant ATB
DaveB
