Hello Andy and welcome to the forum.
To start a window-cleaning business is reasonably straightforward, but it is important to start with the proper attitude and not be afraid of physical work.
For a complete newcomer like yourself, I think you might have a bit of a struggle to find a local window cleaner willing to train you, but you might be lucky. However, there are training courses for new starters which are designed to teach you how to use the tools, safety with ladders, water-fed poles, marketing a window cleaning business etc. These are run by The British Window Cleaning Academy. Having attended their courses myself I would strongly recommend them.
The BWCA is sponsored by the water-fed pole systems industry leader,
Ionic Systems.
Details are available at
http://www.ionicsystems.com (you will see a pop up with contact information)
Among the choices you will face as you start up is whether to use traditional tools (Ladder, squeegee etc at a cost of around £400) or go for the more expensive option of the water-fed pole (from £1,500 to upwards of £6,000). There have already been many good topics on this dilema, and it would be best to have a look through them both on this and the Window Cleaning issues board.
But the most important thing that is needed to succeed in window cleaning is self-motivation. As long as you have plenty of that, you will be likely to do well.
Keep us posted!
-Philip