The .25, .40, etc refers to the cubic-inch engine displacement.... same thing as a 2.5 litre car engine. I believe that .40 is about 7cc. .60 is 10cc, and 1.2 is 15cc

The volume of the cylinder of a .40 engine is 0.4cubic-inches. I am not sure what engine you have, but if it is .020 as suggested, then it is "pretty small".

Flying as a hobby is not cheep. there are ways to do it in a relatively inexpensive way, but I would count on spending a small fortune to get started. Typically, you need instruction (training) regardless of what plane you fly, and this typically rewuires being a member of a club, which typically means that you need to be insured, which typically means you have to be .spending money before you can fly...

In Canada, it cost me $1000CAD to get a .40 size trainer airborne (GBP400ish).

I highly recommend looking for a local club, and just chatting with a member to get a feel for what is out there, and what it will set you back. Speak to the guys at the hobby shop, they will point you to a local club.

It sort of breaks my heart to say it, but RC Airplane flying is not the sort of hobby that can be easily enjoyed on a tight budget. Every time you go to the field you burn fuel, and get tempted to buy something better, faster and more thrilling. I find it depressing when there is something I really really really neeeeeed, but can't afford it. Also, it is risky in that it is really easy to completely trash your plane, so you have to be willing to put your money at risk.

All the best

gus