> you'll need a new keyboard
Not really. I use my UK keyboard to type French. For short texts, I keep UK layout and use AltGr for diacritics (I am on Linux, so in addition to AltGr I also have a Compose key though you don't need it for French). For longer texts, I switch to Catalan layout, which can be used to write proper French (and Occitan, which I also speak) whereas a traditional AZERTY keyboard cannot (the new AZERTY is OK, though I still don't like them plus I was trained to touch type on QWERTY).
PS: When I say I use AltGr I mean AltGr+;, e for é, AltGr+', e for ê, AltGr+#, e for è and so on. I don't mean the insane AltGr + bunch of random numbers that people on Windows are (or used to be?) stuck with.