Would there be space in the cylinder cupboard to mount the pump on shelf, say above the tank or something like that? Or could the cold water cistern in the loft be raised at all? You don't need much head above the pump - as Rob says about 500mm (for the Monsoon pumps, Stuart turner say 500mm from bottom of tank to bottom of pump. Salmander 600mm to the pump inlet. Raising your tank a foot or so would probably give you that.
There are some extra plumbing considerations - have a look in the installation manuals on the pump makers sites.
As to feeding the pump. how much of a risk are you willing to run? there are the various requirements either to ensure there is enough water for the pump (enough flow, damage from water starvation), or to reduce the problems caused by air in the water (damage to the pump from cavitation, more noise) If you don't follow all these things you risk invalidating the warranty. But I've done things the 'wrong' way before, and just accepted that if it goes wrong, I'm on my own.
Well cold is easy enough, you can put in another cold feed from the CWSC. Though if for example the cold just feeds the en suite then in reality it's fine to use that if no one else is going to be using it.
Hot, well Tee-ing off the hot the pipe near the tank is one of the recognised ways of doing it, if maybe not optimal - there are diagrams in the stuart tunrer installation manual. - though should be arranged so air doesn't go up the pump pipe. doing it elsewhere you might get away with it it depending on how the piping is arranged, other draw off, the shower flowrate etc.. There are probably loads of pumps out there working fine not installed in the right way, because manufacturers instructions are always goign to err on the side of caution
But really, it';s not that hard to put in new feeds - assuming that the ensuite is under the loft with the tank in.
