build platform so we can buy stamps direct from Royal Mail and print out ourselves
I used to use Etsy (by the way i much prefer Folksy) but one thing they had which made it a lot easier for sellers is that I could buy Royal Mail stamps direct them from them and then print my own label and attach them to envelopes with weight, QR codes, addresses etc. I know it might take quite a lot of effort on your part but really I think it's worth it.
Debbie Cummins commented
I would also like Royal Mail Click and Drop integration to use my Royal Mail Business account.