thanks for the response. When I create the collage, I have customized a template (3-4 RAW images/template) and then print to file as JPEG. I have set print sharpening to high, media type to Matt, JPEG quality to 100, file resolution to 300ppi, colour management to sRGB. I then try and upload to photobox so I can create a page of a photobook but the image looks really poor. File size for the collage is around 3MB.
Even though you are printing to a JPEG instead of to a printer, you still need to go into the page setup and choose a paper size. I'm wondering if maybe you are creating a 4 x 6" JPEG and trying to print to a larger size.
No I hadn't looked at the page setup and now after doing the page set up I definitely can see an improvement! although the colours are still quiet muted. Thank you very much for taking the time to respond!