As you cross Patagonia from East to West (Chileans generally include the far southern part of their country in the concept of Patagonia), the climate changes from Arid to Very Wet, with a significant transitional zone in the middle, though in some places it is rather narrow. Torres del Paine (which I have visited twice) lies across the transitional area, exhibiting the full range of climates. You can walk from the arid zone to the transitional in a very short time, as you go around a spur and arrive in a rain shadow. So proximity is not a good measure of continued suitability/unsuitability.

Plants from the very wet, cool, but never very cold, west coast of Patagonia (mostly in Chile) frequently do well on the west coasts of the British Isles, especially, Scotland and Ireland, which has a similar climate. Fuchsia magellanica and Gunnera tinctoria are invasive weeds in Ireland. Escallonias are popular hedging shrubs. Berberis is everywhere. Sometimes these species have a wide geographical range and have been sourced horticulturally from much further north in Chile, where the climate is milder, and from this provenance do not always do very well in Britain. This is a specific issue with Embothrium Coccineum (notro), which has an especially wide geographical range. I've seen it growing very well in (inland) Connemara, along side a brilliant Crinodendron hookerianum, and i believe these are also grown in Scotland. Unfortunately I haven't been in TdP late enough in the season to collect seed from it.

The best area for obtaining plants likely to succeed in much of Britain is the Transitional zone, since this area has a wider temperature range and moderate rainfall, very similar to many areas of Britain. This is the area where Nothofagus antarctica grows, as opposed to the evergreen forest on the coast. Plants from the arid zone may not be suitable for Britain, they likely require a wider temperature range than we can give them, and won't like our wet mild winters, but they may be good for places in the USA/Canada where they get that wider temp range, and less wet/humid winters.

I believe the A desideratum you mention has not succeeded in cultivation anywhere, and it seems it is a very fussy plant, as well as coming from the (semi) arid zone unlikely to supply suitable plants for Britain. But you no doubt saw loads of berberis buxifolia (calafate) nearby (the berries of which are popularly collected for consumption/jam), and that is commonly grown in Britain. Unfortunately the form commonly available here doesn't fruit.

I had a walk in a Chilean coolish temperate forest just last year, in an area with a rainfall about the same as Manchester or Bristol, not very far south, but the altitude (5000 feet+) compensated for that - snow in winter, too cold for grapes or peaches here. Almost every plant I saw is in cultivation in some part of Britain - several Nothofagus spp, Buddleia globosa, Fabiana spp, Colletia spp, Gevuina avellana, Chusquea spp, etc.