I think it depends on how you define good conditioning.
One of the best sustainability case studies in the UK is Willie Park Jr's Temple GC in Maidenhead. Temple is - largely - built on chalk downland. Like many courses, tree planting, watering and feeding had changed the nature of the course; less fescue and browntop, more poa and perennial rye.
Some years ago, a number of influential members of the club steered Temple down what, for want of a better term, could be termed the Jim Arthur route. Dry it out, starve it, return it to traditional fine grasses, cut down a lot of the trees.
Now, Temple is, in my book, a very well conditioned course. It is mostly extremely dry, fine grasses dominate, and the playability is excellent. Much of the out of play space has been returned to native grass, with a lot of rare orchids and excellent biodiversity. But of course, there are plenty of people who go there and bemoan the colour of the turf and say that it can be spotty.
But to me, the best conditioning for UK conditions, if it can be achieved on a particular property, is a multistand of fescues and browntops, playing firm and bouncy and with the characteristic spring under your feet. Not all golfers would agree.
The Temple story is well documented by longtime green chair Malcolm Peake in his books and articles. And there are plenty of other courses going down the same route. An interesting project is the ongoing renovation at the Wisley club, an RTJII-designed course (Kyle Phillips was the lead architect) in Surrey. Wisley is one of the few US-style private clubs in the country. They have now rebuilt two of the three nines, under Bobby and Bruce Charlton's supervision; the third will be done this year. Fairways were poa and have been regrassed with a traditional fescue/bent mix (greens are creeping bent). Time will tell whether they can keep the place dry enough to resist poa ingress - they have a very demanding membership, including loads of European Tour pros - but I would say that the conditioning of the new-look holes is _dramatically_ better than they were before, and certainly more sustainable.