Further experimentation with the 3800 and getting hold of Harmans profile for its FBAL gloss paper for said printer and I observe that the Harman paper soft proof shows very little difference - a very slight dulling of highlights - in comparision to the unproofed screen image and on printing is a very close match for the print. I did have to widen the platen distance - as I'd been warned (and also had to do on the 5000. With the Pixel Genius profile for Epson Exhibition on the 3800, there is a bit more dulling of the highlights when soft proofed and again this accurately reflects the print and probably is explained but the reduced gloss of the Exhibition paper.
It would be convenient to print on the paper that most closely matches the screen without soft proofing (and with) - I just have to decide if I can live with the extra gloss. I went through my Lenswork folios again, both black and white and colour and decided that I could live with the gloss for now. I have two boxes of Exhibition and will quite happily use it up.