What factors decide work permit success?

Is there a working formula for work permit success?

Does it all come down to current reputation or are there other factors such as being able to speak the language and transfer fee?

To gain a work permit. The official rules are that a player has had to have played in 75% of his nations games over 2 years and they must be in the top 70. Sometimes a player considered a good prospect can gain a work permit without meeting the criteria too.

just to back up what's already been said, the player does have to play a certain percentage of national games unless they are considered a seriously good player for the league you play in, in which case an exception will be made.

Also remember that its full internationals that count and not Under21 appearances.

Also remember this is only for the English league. Other rules may apply for other countries.

High PA youngsters will often be able to get a permit on appeal. Reputation probably plays a significant part in that decision as well, as a low reputation player's potential would not be well-known and thus not be apparent to whatever governing body makes the work permit decision.

So why does the player get his wp rejected at my club, wolves, and then 2 weeks later he gets a wp at ManU?

That would imply that there are other unknown factors involved. I've always had a gut feeling that the squad status offered to the player affects their chances of getting the permit, but in your example that probably doesn't make sense as I'd expect you to offer a higher status than Man Utd. Perhaps check to see the squad status of the player at Man Utd and compare it against what you offered? It's also entirely possible that your club reputation and/or training facilities may affect the probability. Lastly, I would assume that there is a random component involved which would explain the different treatment.

So why does the player get his wp rejected at my club, wolves, and then 2 weeks later he gets a wp at ManU?

did he meet his international games quota in those 2 weeks?