Fittings are good , very reliable , the 15 mm bends to about a 6" radius , dont know if thats enough ?
Personaly , I would go for 22mm x 10mm manifolds.........10mm to all rads , converting the valves to each end to improve circulation, the existing twin entry valves have an injector pipe that over time corrodes and drops off , resulting in poor circulation.
you should be able to fit the 10mm without having to use bends , or maybe I need to have a busmans holiday ??