OP, I’m guessing that with the price of your phone contracts you also have expensive handsets? In general do you tend to buy branded items rather than more basic ones? It might well be that you can find savings there. It might sound obvious to anyone who’s used to buying mon-brand things, but I think sometimes you can get yourself into a mindset that “only brands will do”. My DH was like this when we first got married - he would only buy branded things, like cereal etc, because he subconsciously believed that the supermarket own brand stuff wasn’t as good- it was only when I bought some and he tried it that he realised it was fine.
So in addition to changing from Waitrose to Tesco/Lidl, look at what you’re actually buying, and whether there’s a cheaper option - for example, Kellogg’s cereal will always be expensive, but for most things Tesco own brand is just as good. Supermarket clothes are fine (if DS is hung up on labels then suggest he mixes and matches with say cheaper jeans and a branded top, and he has to buy the branded stuff himself).
I’d definitely get the house in France generating income, and cancel the cleaner at least while you’re out of work - you’ll have time on your hands to do it yourself. Keep your phone handset once your contract ends, if you can, or get refurbished ones from somewhere like BackMarket - I’ve used them for tech stuff a few times and always had a great experience.
Getting DS on board is important too - you can tell him that you’ve enough money to live on (so he doesn’t worry), but that there’s not going to be much for luxuries for a while; help him to think about what he can do to help - maybe there’s an activity that he’s been thinking of quitting which would save you some cash, or he’ll think about getting a job (or doing some odd jobs) to bring in some money. Maybe he could even learn some basic decorating skills so that he can help out with that. It might make him feel good to feel that he’s contributing and the two of you are pulling together.