I think your best bet is taking accurate measurements, not only of D to D but also front of gullet, middle & back. Saddles vary so much, wide in one make could be extra wide in another. Sorry that does not help you very much. I think wide saddles in particular tend to have flater panels and wider gullets so you really need to measure..
I thought as much...just wanted a rough idea really, been ringing round saddlers to see if they have anything anywhere near suitable and they all ask is she medium, wide etc and i feel silly not knowing! i will have a measure up and give them those instead more accurate. thanks x