After a mammoth trip covering 850 miles in two days, I decided that it would be worthwhile forking out for a replacement seat, in time for my next (even longer) trip in three weeks time.
I'd had a custom seat on a BMW F650 Funduro,and loved it. It was made by CM SEATS of Coventry,
http://www.cmseats.com so I contacted them a few weeks back, to enquire on costs and timescale.
After prompt communications I sent my seat down (it was their first Crossrunner seat, so no templates) and less than a week later it was delivered to my door, all done.

I went for a basket weave style covering, with a gelastic pad for the rider section, and all topped off with red piping. The cost was £220 (excluding my shipping to them).
I've done about 90 miles over the last three days, so here are my initial thoughts.

I think it looks great, without being over the top - a nice 'upgrade'. It is much more comfortable than the 2011 stock seat, which I found slippy and increasingly uncomfortable over any distance of 50 miles and above.
The new seat stops the slide forward, but the gel pad takes a bit of getting used to, as I'm more aware of a floating feeling than with foam. The comfort does depend on your seat positioning and trouser material, and I'm still experimenting. The new seat increases the seat height ever so little, but you can specify a cut-down option.
I was concerned about the potential damage to the seat due to strapping down on ferries, so will need to have some extra padding ready for this.
So far it's a qualified thumbs up, and I hope to report after the real test later next month - watch this space!