As far as Brentford's BMW go:
Benrahama is the easiest to get out of the three Villa defnitely wanted him in the summer but baulked at the £20m price tag put on him but all the noises were that if someone came in with close to that he'd probably push for a move. In terms of styles of play I'd put him as the Championship version of Eden Hazard, similar build and similar silky dribbling skills. Started the season a bit slowly but was recovering from an injury and maybe ruing the fact he didn't get a move to the Prem. Plays wide of a very fluid front free so who would he replace at United - probably Daniel James. Obviously not as quick as James but will score and assist more than him I'd wager. Given the league position and conrtact he is on it's going to take at least £20m I'd say to get talks going.
Watkins believe it or not is playing his first season as a centre forward having joined as a wide attacker and having been played as one for the last two seasons. To be honest it started slowly for him and lots of fans doubted he had it in him to play that role despite Dean Smith's, Thomas Frank's and Phil Giles' (one of rht DOFs) insistsnce that he would make the tranistion to CF at some point. He has been superb in the role though and his all rund centre forward play has improved immensely. He can hold the ball, bring others into the game, scare the life out of defenders with his pace and strength and most importantly put the ball in the back of the net. However who's he going to replace at United and to put him on the bench would be a crime against his development. He also signed a new contract in the summer so again you are looking at £20 plus million to even get talks started.
Mbuemo - now this lad looks top draw, pace, skill and can finish. It raised a few eyebrows in France when he moved to the Bees as he was considered the top talent outside of Ligue 1. In a league like the Championship that is notoriously tough to acclimatise to this lad has 10 goals and 4 assists already. Considering it took Maupay a full season to get up to speed before his amazing feats of last season this bodes extremely well for his future development. I'd say the chances of getting him in January are zero unless you are talking silly money.
All three are technically very capable of playing in the Premier League but I hope they'll be doing it for Brentford in the very near future if not then I am sure it's going to cost the buying club a pretty penny to get them.
I'll just leave this bit of filth here - I do love Benrahma and his ability to embarass: