St Germain is definitely worth the visit for anyone in the Paris area, I think it dates from 1921 and I don't think it's been tampered with at all. It is NOT overgrown with "broom" or anything else. It's not over-manicured, but probably it's like the architect intended. The old original push-up soil greens are pure Poa annua - fast, true, and smooth. Bunker placement may be described as "quirky", as most holes have some located within 50 meters of the tees. A few of the holes are a bit flat and non-descript. It's short by today's standards, but a joy to see and play.
In France, at least, there are a number of Colt and Simpson designs still more or less intact, I hear. I'm sorry I haven't gone out to visit more of them yet.
Anyone interested in golf in Europe would do well to start with the Peugeot Golf Guide, published by D&G Motte in Switzerland. It lists about 1000 European courses with (English) critiques, descriptions, locations, contact information, architects, dates of openings, and a rating scale (not the Doak one). The Guide is available in Pro shops in Europe, but I don't know how you get it elsewhere.