Looking for alittle guidence if possible.

Hello again guys, after so much help recieved on my last query i wanted to ask another two questions, firstly after working out the legnth, avoiding volt drops so on and so forth and correctly calling the sparky for extra guidance as i couldnt give enough infomation here, (sparky call was just some of the the advice by the way) i wanted to know because im dumb and didnt ask him firstly would it be recommended to swap the electric shower for a gas one which i have been told is more than possible as the layout and internals make for an easy fitting, (accordinly). (and that question comes from the sheer amount of horror stories ive heard from them)? Secondly does anybody know as it reduces the cable length dramatically wether going over head and having our weston power distribution company connect it to the mains for us as a seperate supply would be more or less in price than going from the mains to the house and then out to our static? I dont know if it make a difference knowing but option one, going over head theres 30 meters of 16mm 3 core internal earth cable, and option two goes from mains to house then to the static which is 120 meters of cable? I hope i have worded this well enough to understand and like last time thankyou so much for even taking the time to read my post i can hopefully provide more infomation if needed. 

Drewboards. 

A WPD pole transformer and new supply will cost quite a lot - get a quote.

Can't comment on gas showers, but they have been popular in caravans for decades (I'm guessing you mean bottled gas?) 

Have you considered a water tank and small wind tubine / solar array (ie off grid)? 

We lived in a static caravan while doing our self build.  It had a 10kW instant gas water heater that ran the shower but to be frank the flow rate at a decent temperature was pretty poor, allowing for efficiency of the gas boiler it was probably only about 7kw of actual heat, so equivalent to the very smallest of electric showers which would have a similarly poor flow rate.