Shower Installation

i want to install a shower for my house. i don't have an existing shower so theres nothing already in place. The heating system we have is a fire place / back boiler in the kitchen. In the airing cupboard theres a hot water tank and above that is a cold water tank but i think this is used for the central heating as the water inside this tank looks like its been stationary for a while and unfit for tap water. I think all cold water taps are feed from the mains.
Is a thermostatic power shower plumbed from the bath pipes with a pressure equalizing valve ok? as i already have a thermostatic power shower and would just need to purchase the PE-valve and install?

I don't want to have to install a electric shower as the fuse box is located 2 floors down and to power this would be a big electrical wiring job.
If any one could help i would much appreciate this.

theres pictures of my airing cupboard tank etc.. are available here:

http://www.koolmobile.co.uk/ch/

Should be ok. I haven't been through your photo's but the tank above your cylinder will feed your hot taps, if you look in your loft you will notice another tank, this should feed your heating.

even though the cold are fed from the mains? or is this where the pressure equalizing valve plays its part? do you think the hot water tank would be addequate for a plentiful supply?

Yes the equalising valve will sort out the differential water pressure.

Yes you should be ok with the water header tank, try and fit your pumps etc in airing cupboard, and make sure the hot feed to the shower is a single pipe run to the shower, don't tee off the hot water supply if you can help it.