Sorry for the delay in getting back to you. Thank you for the work you have put in to rewriting this extension.
I have followed your instructions and the set up looks great. But I have a problem that the extension wont stay installed. By this i mean it installs, all the settings are there and I am excited because I can edit the costs if necessary, but when I go back to the extensions page it shows as not installed.
I have tried deleting it, uploading again and clearing the settings and cache as described but it is the same.
And I have tried processing an order on my site and it doesnt show any Royal Mail shipping options, so it really isnt there.
Any ideas