Hi Ian. Being in the U.K., have you even considered a Bosscreen? http://www.stabitech.nl/Bosscreen.ht...eenGroundglass
It might be too expensive for your needs. (approx. 94 GBP) I replaced a older Beattie, with a Bosscreen on my Linhof Tech. V 4x5, and it's soooo nice. Due to it's unique design, there's no granularity or hotspots with the image. Very easy to focus too.