I never imagined that the hobby I had was so popular before I cam to this site!!!
Splitz - I have been through exactly the same route that you are currently on! from all that i have read you have made considerable progress on the basic elements of RC flying. As suggested by someone, first the free flight (just chuck), then the powered flight (with motor, prop and battery only) and then RC - thats the only way to get there with the small planes. Considering your motor size and wingspan and with no offence to whoever has made the recommendation - dont waste your time with the CR 2032. that will never fly your plane simply because of the weight. A 2032 (or two of them coupled) maybe good for a 15-16 inch wingspan with a 4 odd inch width, not for yours.
Your choice of the china make mini heli is bang on the mark. Those models have everything you possibly need. Theres one specific model that will be a great help. It comes with two main motors driving two rotors in opposite directions and one tail rotor (the best way to identify is to look at the tail rotor, it will be pointed upwards and not sidewards for these helis and you can see the two main motors). This heli will have three motors in all and the right circuit which you can use the differential on a biplane to turn. The props from the mini heli do the job more often than not, but at the same time if your are looking at improved performance and you are patient enough, carve our a prop out of a 2mm or 4mm balsa sheet(for the biplane the tail props will be good enough). the battery in the china heli is not more than 1.7 odd grams and the main motor is of similar weight. You can use 1mm balsa for the plane too. Incase you need even smaller battaries (and since you are in Mumbai) you can visit Lamington road and in the lane opposite Ayodhya hotel theres a navjivan battery store(its a typical "baakda" on the road, the aarey milk stall type). They have 30-50 mah lipos that weigh around a gram and will cost you Rs. 150
. Superb for your stuff. The best source of the motor is the link provided in this post. And yes, the china helis are now on eBay.in for as less as rs. 500 and you can also visit crawford market (specifically behind manish market, near CST station) and buy these china helis for as less as Rs. 400 complete. Incase you decide to use button cells, anything more than a g1 will be a load and g1s will drain faster than you can wink!!
You may also like to consider using the tail motors from the mini heli as your main motors. They are powerful and lightweight. Your total weight for the equipment (if you want to make a 6 inch wingspan fly) should be :
Lipo - 3.7, 30-50 - 1.5 gms
Main motor (simple plane) - 1.7 gms
Motors (each, bi plane) - .8 gm
Prop (single) - 2 inch, .5 gms
Props (Bi) - 1.2 - 1.4 - .6 gms (the heli tail rotor)
Rx - 1.3 gms (from the heli again)
Plane - Balsa frame with kite/tissue paper - 1.6 - 2 gms.
And you will have the total weight at around 7 odd grams.
Finally, for the bi - plane the prop and go directly on the motor, but for the single motor plane you might want to consider a gear ratio (you can use the gear from the china heli too) to increase thrust. Hope this was helpful.
Andy