Nellycopter,
There is a good reason that training has to take place on an airfield and it is nothing to do with long runways.
Proportionately more accidents and incidents happen whilst training. If you train at an airfield you are going to have someone watching what you are doing, be it a Flight Information Officer or full ATC. If you get it wrong even in a small way, they can raise the alarm or simply enquire if you are OK. Even better if it does go very wrong there will be Fire and Rescue cover available to quickly come to your aid.
If you fly around in fields, they are likely to be away from habitation so you do annoy anyone. If it goes wrong then, even if it is a survivable accident, you may not get help for hours and I have even seen it turn into days. It is surprising how a forest can swallow an aircraft and leave no trace.
Thats why the CAA (and any sensible Authority) stipulate training at licenced airfields. It isn't designed to generate them funds (for a change) it's for your safety.
So once you have learnt to handle the aircraft in a large safe area then get your instructor to take you to your operating area and show you how to safely operate in and out of it.
FNW