This particular installer wouldn't use it on his customers.
Fernox every time. It will be double the money, but pay the price, do the job properly. Many other pros on here would agree. Hope our customers appreciate it.
If your installer is using this stuff, you can be assured that everything fitted will be the cheapest option they can buy, apart from the boiler because they told you which one you were getting. TRVs, controls, fittings, radiators, Zilmet expansion vessels; it will all be the cheapest stuff the merchant can offer.
PS: My supplier switched a Little Giant condensate lifter I'd ordered last year for an Instinct branded one on a boiler installation. Lasted all of 12hrs, had to go back the day after and change it out for the one I'd ordered.