Plant garlic, cloves, cilantro, arugula/rocket, and Asian greens like bok choi and mizuna. We moved here last July and those were what really thrived in my much-neglected garden and fed us into the winter. If your climate is mild, you can plant spinach and have it overwinter, but mine has never made good growth in the fall. And of course lettuce. I did my planting late August/early September but we had a long summer last year.
Coastal parts of Brittany are the equivalent of USDA zone 9.
This should give you plenty of opportunity to get in some plants that do not like hot weather before it cools down too much in the autumn.
Green peas should do well if you give them some shade until it begins to cool off.
I was also planning on 'cardboard mulching covered with compost' on the 'overgrown bits.
Should I cut the undergrowth before leaving in place and covering with cardboard then compost, or just 'flatten it down. I've previously cardboard mulched over relatively short grass without cutting first, but some of the grass is chest high.
Also I am reluctant to cut back the blackberry runners because they look like they are going to produce a lot of berries. I was going to let them 'poke through' the cardboard and then cut them back once harvested. Am I being optimistic about being able to take control later?
I'd cut the overgrown bits as close to the ground as possible then lay them down (chop & drop). Re: the blackberries, they do tend to take over, it could be a difficult fight to get them out of your garden, but then again it all depends on how much you like blackberries - they are more nutritious than a lot of vegetables!
Location: Currently in Lake Stevens, WA. Home in Spokane
Personally, I love blackberries, but here in the PNW (Pacific North West), they are considered an invasive. Once they take over, there seems to be no way to get rid of them, other than bringing in some pigs.
If you can train them to a trellis, they are much easier to harvest, and control their overgrowth. Some blackberry jam is a wonderful way to enjoy them all year long.
If you hurl in a few french bean seeds you might see results ... if you get a long summer/late autumn. You should get your first frost arriving quite late in that part of the world! The western edge of Europe is good for bean crops because of the rainfall.
Thanks for all the helpful replies. The Sycamores do provide too much shade in as they are on the South Eastern border so much of the Garden misses out on a lot of sun. There is a lot of land that is totally shaded under the boughs.
The Sycamores are from the next door field, but I can trim as much as I like.
Any suggestions? What can I use the cut off bits for?