Are Ryanair back ? OK.
I do trust that Air SW have done their marketing correctly and know where their traffic on LCY will be coming from already. Normally on a business route you will find that half your traffic comes from no more than 10 or 20 firms, all of whom you should have been in substantial contact with to understand their requirements and likely demand. You can then extrapolate to the total likely daily demand. Air SW should have a good idea of this demand from their Gatwick route. It's not as if you can just start an operation and then sit back and wonder who is going to use it.
Who is No 1 business user to Gatwick for O&D traffic at the moment ? MoD to/from Plymouth ?