I have used your site and found a diamond on James Allen I am very happy with. I am now trying to decide between purchasing the diamond on its own and getting a local jeweller to hand make the ring -or- saving some money and getting the complete ring from James Allen.
I am looking at very simple 18k yellow gold with platinum setting solitaire styles and will probably need to get the ring resized at a later date, my local jeweller says a handmade ring will cope with this better than a cast ring from James Allen. He also says a handmade ring will be much harder wearing and better in the long term.
Price for Handmade: ~£1000
I don’t think there’s much benefit going with handmade over cast for a simple solitaire.
However, there might be a benefit with your expected resizing. Even though JA has free resizing, you still have to ship it back them and wait for it. I resized my wedding band with them and it was free shipping both ways, but I’m not sure how that works for items shipped back and forth to the UK. In that case, it might be more convenient to have that done locally. The turnaround will also be faster if any further tweaks are necessary, like a quarter size up or down.