Slightly odd question. We are looking at houses round Kilmorie/Cranston/Como Rd areas and every one we have seen has an electric shower rather than mains style power shower in 1st floor bathrooms. All houses had combi boilers. Is there some water pressure issue in the local area that stops this? Or another reason?
Combi boilers can reduce the pressure of the water supply, and as most showers require good pressure the use of electric showers is a solution. That said some of the better made showers can work on 1.0bar pressure but cost £200+ bath/tap mixers are not always successful. So if you want a shower that pins you to the wall you need good pressure hence mains power. There is also the argument that heating the water in the pipes to the shower and the time to reach temp is wasteful as opposed to instantaneous.
You can’t have looked at every house on the market then 
We’re at highest point on Cranston and have combi boiler fed large head/rain style showers on both first floor and second floor loft conversion. No problem with water pressure unless you run both at once but that’s more of a combi boiler limitation than water pressure issue.