Shower pump / mixer valve

I have a question or two (well three) about a "power" shower I'm about to install and would be grateful for advice.

I'm in a single floor flat so there's not much of a head. The tank is next to the bathroom so at most there will be a 3 or 4 metre run of

22mm pipe (stepping down to 15mm near the mixer).

I already have a new twin 1 bar pump (aquaforce 1). In an ideal world I'd already have a new twin 3 bar negative head pump, but I don't, and the one I have was free so I figure there's no harm in trying it first (I presume a future upgrade would be more or less a straight swap)

Question 1: Any idea what sort of positive I'd need to get it going automatically? I estimate the "normal" position of my current electric shower head is 10 cm below the top of the water in the tank (float valve already adjusted to the max). Could lift tank maybe a further

10cm - but that looks a lot of work. I've lived somewhere with a separate switch and hated it, I'd rather just buy a negative head pump.

Question 2: It would be easier to run the both the bath taps and the shower through the pump to save doubling up on pipe runs around the bathroom wall. Is this a bad idea?

Question 3: I'd lilke to avoid having the mixer valve under the shower head to avoid having to stretch around the shower screen to turn it on only to get an arm covered in cold water (it will be an overbath shower). I'm think putting it on the side wall will bang my elbows when showering. Is it a bad idea to put it at the opposite end of the bath and running the output of the mixer through a length of 15mm pipe behind the wallto an output at the other end. The overall pipelength from water tank to shower head will be about the same, but the mixer valve will be half-way along, rather than near one end, and they'll be more 15mm pipe).

Thanks for any help! Darren