At one level, you have this already, I assume you have some broadly equivalent roles. You pay a general manager in the UKX and in India Y. You could use these to do a calculation on what to pay.

Personally, however, I would simply ask the Indian management team to make some recommendations on what they think would motivate people to recommend colleagues. If necessary, I would start a six-month trial, and pitch the benefit slightly low so I could move it upwards if needed.

I don’t think there is any science or real method behind these payments. They are just pitched where people think they will work.

I'd do what Keith suggests.

Start by asking your Indian manager/s.