The Quartz Thermostatic Riser System is one of a number of showers which customers have problems with. This shower mixer retails at around £270 and looks nice, but it could give you problems.
The retailer Victoria Plumb does not mention that the Quartz Thermostatic Riser System is unsuitable for gravity systems, but in the specification does mention that the minimum water pressure required is 0.5 bars (5 metres). An upstairs shower will typically have 0.1 bars.
The SP2B Shower Power Booster will increase the pressure by 0.4 bars, which with the 0.1 bar you already have, you will achieve the minimum pressure. A minimum shower pressure will never be great, but if you are looking for a cheap quick solution a SP2B will sort it.
One problem you could have is that before the pump starts you could have too low a flow start a pump automatically. You need 1.5 litres a minute to activate the SPB flow switch.
You might achieve 1.5 litres a minute if you lower the small hand held mixer head low but the only way to check is to use a measuring jug or collect water and weigh it (1KG = 1 Litre).
If you cannot get 1.5 litres a minute to activate the flow switch then you can:-
1.0 Plug the transformer into a 3 pin socket and turn it on and off when you need it.
2.0 Wire the transformer into the light socket so it comes on and off with the lights (or an extractor fan)
3.0 Buy a radio remote to make it ‘semi automatic’
Making the flow better
Putting 2 pumps on the hot will double boost the pressure so you will have 0.9 bars.
If you want to maximise performance you can either buy the 2 pump SP21S kit if you want to maximise the performance or if you have already bought a SP2B you can add a second pump by buying a SP1U Upgrade