Ok,
I have read the manufacturers guidance and there is nothing suggesting gravity fed is suitable, please quote.
No the builder would not need to be electrics qualified, please look at the advice from Which, I cant post the link as the forum wont let me.
The person did not need to read the instructions as it is very basic, drill four holes, secure shower, connect pipe, wire the same as a standard plug.
No red flags, job done at a reasonable price, the shower failed as it was not sold as described, the fitting was not the issue.
The shower was fitted in accordance with the manufactures guidelines even though they weren't consulted, even if they had been referred to that part of the booklet is past the compatibility piece which is the real issue, the shower failed to work as the water pressure was not sufficient.
I did return the product and was refunded as the item was not fit for purpose/sold as described my issue now is consequential loss.
In summation:
1. Was the shower advertised as suitable for ALL water systems, Yes,
2. Was the shower fitted correctly, Yes,
3. Did it work, No,
4. Was this due to the item being installed incorrectly, No,
5 Was the shower sold as advertised, No,
6 Had the instructions been read from cover to cover in spite of the advertised suitability would the shower have been fitted, No,
7 Would I have still been charged by the trades person for a call out, Yes,
8 Are Argos at fault, please comment......