If your electric shower (normally a white plastic box on wall) is not working it is normally not worth repairing unless it is only a few years old and did not cost more than £250.
Electric showers do not tend to last more than ten years at most and quite often last a lot less than that. In most cases the shower manufacture is needed to repair the shower instead of a plumber (you could well have to wait a week or two) and they would then only guarantee the part that has been changed so the shower could fail with another problem weeks or months later. A new shower would work straight away and if it is close to the old shower would take around a hour to fit. Also the shower would have a manufactures warranty (mira and triton showers have TWO years).
However electric showers are piped and wired differently (wire and pipe are not in a standard place)so the secret is to either get the exact same shower or to check the position of old shower pipe and wire and then get another shower with the pipe and wire in the same place (research on internet or remove the cover which is not recommended if you do not know what you are doing due to the real chance of being electrocuted (plumbers know the pipe and wire positions with experience )the reason being that a hole would have to made in the tiling or aqua panel to shift the pipe and wire which could well be a big hole. Also showers have different kilowatt ratings (7.5kw to 10.5kw)and if you get a new shower with a different kilo watt rating a electrician WILL have to change the circuit breaker to match the new size. Therefor with pipe , wire , fuse boxes having to be checked , water to house switched of and drained ,water connection maybe being altered It is not recommended for a d.i.yer to attempt to change a shower themselves due to risk of flooding ,electrical fires or electrocution .
I hope this information has been of some use and of course your local ,friendly, Aberdeen plumber would be more than happy to help you out.