They don't need to be Genuine. Britpart springs are very good. They do a standard ride height heavy duty spring which will have the effect of lifting about an inch over standard. They also do +2" springs.
I have Bearmach springs on my Disco. They are fine but some of the later batches have been known to break! I think they have sorted this but you don't know if what you are getting is old stock.
If you don't want to buy longer dampers you can get mounts which will lower the damper the required amount.
Please note that is is nigh on impossible to say how much a set of Defender springs will lift a Discovery without trying it. You have to consider the weight of the vehicle and max load. Whichever is higher will have a stiffer spring. Although there is little load effect on the front when loading the back of the vehicle, the front springs have to support the engine and most of the gearbox. V8s are quite light in comparison to diesels. I don't know if you can get diesel spec springs over there.
I know your resources are limited and springs and dampers are very heavy and can't easily be shipped over.