I ended up just carrying the backpack around with me by the handle (WCW) or the straps (shurflos), no trolley. Never used it on my back, could see it being a strain all day.
The wiring and switch were rubbish on the shurflo, agreed.
John hewitts is getting my vote at the mo. don't need a controller, just use a tap on end of pole so will probably rule out gardiners at the mo. and the new WCW ones seem to have issues!