I would have loved to see all the saxifrages at Waterperry, but after some debate decided I needed to get on with a very large pile of material that needed shredding - must put it down for next year. As regards labelling - we have the same problem recording plantings in the garden and in the past I drew diagrams (cf: those illustrated in this thread). These were OK for me, because I already had a good knowledge of what was where, but others I think would have had trouble deciphering them. Now that it is so easy to take digital photographs I use this as a method to record new plantings, and it is a lot easier to relate to what you see. This is pretty much what David suggests. Different sections of the plantings can then be related to specific photographs of each area. This is obviously especially important with plants like saxifrages where so many hybrids have been raised.
I've been toying with the same idea for our sand bed when the garden is open for the NGS and AGS; otherwise any labels that are there get pulled out and stuck back in willy nilly (or sometimes if someone is really interested, taken away!).