Did you see the photo of the one I've got in the niche of our new wall? That firm was excellent, and had lots to choose from. It's Taylor's Garden Buildings. I found them online - and ordered it online, too. It came very quickly.

I can recommend Agriframes. Not cheap but excellent quality. I've had two arches for over twenty years - one of the has been supporting two wisterias (which is no mean feat)

Thankyou both very much for the advice. I have seen arches from both these companies. Glad they are good quality. this is why I asked on here. personal recommendations really important.

I can also recommend Agriframes, my arch is 12 years old and shows no signs of deterioration. I also bought the diamond shaped infill panels (which at the time of my purchase were optional) and they have made tying in the climbers really easy and look attractive in the winter.