Lippy, I'll have a try...
Changing over from using ladders to a Water-Fed-Pole (WFP) is without doubt a daunting task. What system should you get? What van to buy? Do I need a van? What reverse-osmosis unit should I purchase? What's reverse-osmosis!!!!!?
If you've a mainly residential round and plan to do 'tops only' with a WFP then the Shurflo back pack is a good place to start.
The whole set-up has to be purchased individually and should cost you around the £500 mark.
You can buy the Shurflo back pack from here:
http://www.williamsonpumps.co.uk/Mine cost £215 including VAT and postage.
You can also buy them from E-Bay USA for around £160.
You'll also likely need a Reverse Osmosis (RO) unit and you will need a DI unit.
You can buy these from RO Man, (the unit in the link bellow would probably suffice), depending on how much water you plan to use. Doing 'tops only' I use around 100 to 150 litres per day (it's four litres to a gallon by the way.
http://www.ro-man.com/shop/product_info.php/cPath/22/products_id/30You'll also need a pole. I suggest an 18" one if you're mainly doing 1st floor windows. You can get these from numerous places, but this site generally gets a good rating and has an excellent 'frequently asked questions' area which explains just about everything you need to know to start using a WFP.
http://www.gardinerpolesystems.co.uk/You'll also need a static tank, I use two 200 litre water butts, at least six 25 litre water barrels and a hand-held TDS meter (£13 approx).
Also, don't forget to ask lots of questions here. I'm definitely not a WFP expert by any means.