Thank you all for your multiple replies...so much to read, apologies for not coming back sooner (like Matteo, I'm polite). Among the reasons why he could come to Villa, I'm surprised nobody mentioned your shirt (one of my favourite Europe-wide).
Pay 40M and I'm almost sure he's yours, unless Guendouzi himself refuses. I'd be really sad should he leave, but unfortunately I know OM can't refuse PL's good money.
Guendouzi's refusal, if any, would not be a lack of consideration for Villa, but rather a wish to go on here IMHO. OM is on a very exciting trend: second last year, currently third (with 42 points at mid-season) and playing its best football since its last champion title, or even better. No more European cup to play, unfortunately, but it may be our chance to keep an intense rhythm till the end of the season. Five points behind QSG experiencing difficulties since the WC (two losses in three games, against 2nd and 5th of the league): who knows what could happen if QSG collapses... Guendouzi may wish to see the end of the story before going back to PL.
If you can afford 40M, you should pay them. You'll like Guendouzi, he's a rather complete player, hard-working, with a strong personality. No attitude problem from my point of view, but he likes trash-talking other team's players (without blowing a fuse himself at any time - no red card since he's been with us). He's the kind of player you love in your team and hate when he plays for another team. Kamara and him know each other very well and are complementary - they have played together for the whole season last year. They seemed to get on well.
I'm also pretty sure OM won't take Samson back as part of the deal. Never a good idea to go back with your ex. And Samson doesn't seem to fit with our current level.
Don't expect too much information until the deal is closed. OM's management has proved over the recent years that they prefer working quietly.
I hope we'll keep him a few more months - at least, don't be stingy if you get him. Remember you got Bouba Kamara for free. 40M for Guendouzi would make an average 20M for each of them, that would be a gift.