Extra cw tank for pumped shower?

Our cold water tank is squeezed into a tight cupboard in a converted loft with no chance of running a dedicated pipe from it to a power shower or pump. Is the best solution to put a second cw tank in the airing cupboard (which is quite big) to feed the shower/pump along with a dedicated feed from the hw cylinder? Is there a minimum distance/drop required from cw tank to pump?

Not really because you want the hot and colds to the pump to be balanced. Is there really such little room that you can't cut another pipe into your existing cold cistern and run plastic from it?

No, it's a bit of a mess. The loft conversion was done about 20 years ago & it looks to me as if the cupboard was built around the tank - there's just no room to get at anything other than the top and a bit of the front.