Hello pagan and hirnyk
Thankyou for your suggestions.

hirnyk
I have seen that the standard error is only available for the linear fit. I assumed that is because for a linear fit this is a straight-forward quantity to calculate. So, I do not think I specifically mean the “standard error” but instead some kind of estimate. For example, by taking the derivative of the w.r.t chi-sq. Any ideas?

pagan I have implemented the module you suggested. This does give me some usefully quantities, but I do not know how to calculate the error of my parameters from them. Could you advise me further?

Thanks to you both

Dan.