score:3
That's five questions.
Is there likely to be any problem drawing cash out when I arrive?
No.
Are there any restrictions on taking any unspent notes/coins out of the country?
Not that I'm aware of, but I wouldn't necessarily be.
Is the CFA franc actually used in practice or am I better taking some cash in dollars etc?
Yes, the CFA franc is actually used in practice. I never spent a single dollar while I was there, and I didn't get the impression that people would prefer dollars. It's probably possible to use them, but you would likely get a less-than-favorable exchange rate.
Am I likely to have the option to use my debit card to pay in restaurants?
Upscale restaurants aimed at the international community generally accept card payments. Less expensive restaurants are less likely to do so.
Are there any obvious reasons not to do so?
None that are obvious to me.