ProPhoto vs sRGB
If I then save as jpeg, leaving ProPhoto 16 bit selected, are there any implications should the client wish to print these photos in a highstreet photo lab or display them online on a website?
I agree with Bob, it would be safest to save them as sRGB JPEGs, which can only be 8 bit, unless your client requests otherwise. It is often to save them in a couple of sizes: full and one suitable for web display.
There are no monitors out there that come close to Kodak’s ProPhotoRGB gamut and of all the common browsers, only Mozilla Firefox is well enough color managed to deal with ProPhotoRGB. Microsoft’s IE will display them well enough, but Safari and Chrome will be at a loss and will display them terribly. Also, many print labs will assume sRGB.