If you have the money buy cast iron rads - I bought some for a job from (Castironradiators) and they are good, keep the heat and the HO is pretty accurate id say.
Exactly this, look nice but HO is miles from what they are saying it is. I'm having this issue on a job currently! Thankfully I didnt supply them but they blamed everything bit the radiators.
Unless it’s a friend you should expect to pay them. Still a job even if it’s looking at something and giving your expert opinion on it