A quick tip if your pump seems to run every time you use a little water.
The pumps that sit on a big metal reservoir, especially the €100 Bauhaus / Leroy types will lose their air pressure over time. Inside the tank is a flexible bladder and it uses air pressure to maintain water pressure without having to continuously run the pump. You can repressurise with a car tyre air pump on the valve at the back of the tank. The trick is - to take off the water pressure on the other side. Switch off the pump and open a cold tap. If all the air pressure has gone then the tank will be completely full of water. As you pump up the air again the water will be expelled from the tap (so leave it open). Pump the air up to about 15psi / 1 bar. You should now be back to normal. If you don't open a tap then you won't be able to fill the tank with air.
If it fails again within a month or two then you can assume that the bladder has a leak - sorry nothing to be done with that as they just don't repair.

Hope this helps someone. 

Thanks Bruixot, where can one obtain replacements? I'll keep a couple in stock.

Found this, seems reasonable at £14 with free postage.
http://www.ebay.co.uk/itm/331858109045