Hang on OP. I hope you do realise that M1 is TSE is not nearly at the level you need to start a PHD. This is undergraduate level stuff. The base at TSE is at the M2 level and then there is the MRES afterwards.
Is TSE enough good to allow grad students to do their PhD elsewhere in Europe ?
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M2 is first-year PhD program in most other places, so with M1, you're well-prepared.
After M1 is the best time to leave because M2 will be more competitive due to PhD admission at TSE, so your grades will likely be (even) worse.
I would suggest you ask your professors whether they know some faculty at the places where you want to go and if they would write you a letter. This should alleviate the mediocre impression from grades alone. But most importantly, leave before M2.