Is a two speed series 3 landrover wiper switch the same as a series two landrover wiper switch?

No. The series 2 and 2a had single speed wipers with the rotary switch in the middle dash. The early series 3 has a single speed rotary switch on the right of the steering wheel, and later ones had a two speed switch. That said - nothing stops you putting a later switch in and using a two speed motor on each wiper arm (series 2 have two motors, series 3 have one and a drive cable.)