Hi Tony,
Don't know about the Machine Mart ones but I use one I got from a supplier in Ireland. My at-the-tap pressure is about 2bar; post booster pump it's 8 or 9 bar. This fills a 500l tank (RO and DI) from empty in 2-3 hours (to be honest I don't time it as it's an end of the day job I do whilst I'm doing my books). Tapwater TDS is 80-100ppm; post RO TDS is +/-3ppm; post DI 0ppm. I have a float switch in the van which shuts of the Shurflo pump in the van via the flow controller. This then allows pressure to build up on the booster pump after which the booster pump's pressure switch kick in and turns it off. I then switch it off at the mains to save the booster pump pressure switch. You must get one with a pressure switch.
If I didn't have the booster pump it would be hours to fill. A booster pump is up there with an SLX, swivel angle adaptor and a flow controller in terms of necessity, for me at least.
Hope that helps.