On the few occasions Flamini played with Cabaye we looked good in midfield. Problem was the Ledley and MacArthur aren't really very good defensive midfielders, they like to get forward too much (I like MacArthur, but he's more an all round midfielder).

And Cabaye doesn't have the power to be a defensive midfielder.

"One Nation Under God, has turned into One Nation Under the Influence of One Drug"
[Link]

It would cost far more to replace them than selling them would bring in. It depends whether the manager rates them, of course, and whether they fit into the way he wants to play, but you're not going to buy better premier league players for the money they would bring in, and untested players from abroad can be hit and miss; some work, but plenty of others don't (see West Ham's recent signings for example).

Continuity has it's merits, and change for change's sake doesn't make too much sense from a player morale point of view. I'd say keep both of them, at least until January and see what the new manager can bring to the team until then.

I used to be immortal

Not IMO.
Both unlucky to lose there starting 11 positions.
See what Frank does.

Palace 13th 2017/18.

Really. Mcarthur was dreadful the turn of the year

Another Damien Diagonal - Total Football

I would accept any bid of 7.5 mill onwards, one year left on contract, has been poor for a long time.

Upgrades on these two will not be as easy to find as you're suggesting.