You don't require a UPS3 even though you can choose a mode suitable for 8 rads.
I have 10 rads with a 6M Wilo Yonos Pico (around £120) which gives great control as the constant pressure (CP) and proportional pressure (PP) settings can be incrementally set between 0.5M and 5.5M which can be quite useful if a open vented system is installed, a 6M DAB2 might also be suitable.