I have a 400L tank in my dispatch. I have these tank fixings from cleantech:
http://www.cleantech.co.uk/catalog/product_info.php?cPath=22_25&products_id=90Took it to a local garage and got it installed for £80.
Bought a leisure battery from halfords. You can use just a pump and control the flow manually with a tap between the tank and the pump.
Or you can get a pump controller to do it.
Cleantech do pump boards for £213. Someone posted a couple of weeks ago about finding flojet pump for £85. These are i think the best pumps (very few problems with flojet pump posted on here over the years).
You just need a a switch to turn the pump on and off. About £3 from halfords.
Ask around here for cheapest place for tank as i don't know. Cleantech is a good place to start for most if not everything.
And gardiners for the poles. I reckon around £1k. But if you can afford, spend £1k on 2 poles from gardiners. The superlite being the main pole.
If you want a cheap disposable type pole, 17ft xtel is a fantastic little pole for ups and downs. For 6 months anyway. Mine lasted a year.