What a blast! You guys kick! All right, I've reconstructed the melee based on all our posts, and found it necessary to have the leader hold 20 extra horsemen in reserve. I'll break this down into four "pictures".
Picture 1: initial layout (I've taken a few liberties for organizational purposes):
Thoronmir is in front. On his right flank is Falowik, who leads tethered a half dozen horses. Uien rides behind Thoronmir and next to Falowik. Lumiel rides just behind Falowik's horses. On Thoronmir's left flank is Finéwen. Eswen is just behind Finéwen, with Lira taking up the rear. The three hobbit ponies are surrounded by Uien in front, Lumiel on their right, Eswen on their left, and Lira in back.
They are faced with three hills, one in front (west), one on the right (north), and one on the left (south). The enemy are in companies of 10. We'll call them Companies A, B, C, D, E, & F, with G & H held in reserve. On the hill in front of them are 21 horsemen: the leader, and companies C & D; to their right are 20 horsemen, companies A & B; to their left are 20 horsemen, companies E & F. The leader holds a reserve of another 20 behind the hill, companies G & H.
Picture 2: first phase of the brigands' attack
Uien, Anson, Gorby, Falco and their mounts, and the six horses, are surrounded by the others. Company A charges Lira and Lumiel. Company B charages Lumiel and Falowik. Company C charges Falowik and Thoronmir. Company D charges Thoronmir and Finéwen. Company E holds back. Company F charges Eswen. The elves shoot arrows and take out 3 horsemen each from Companies A & B. Lumiel and Lira each kill 2 of Company A by the sword. Falowik kills 1 of Company B. Eswen kills 2 more of Company F. Thoronmir kills 3 of Company C. Finéwen kills 2 of Company D. Falco spends his energy making sure of all those wounded, so he gets no kills per se.
Then Lira takes herself away from the fighting to check on Gorby and Anson. Meanwhile, Lumiel kills 2 more of Company B. Falowik kills another of Company B.
Company A: gone
Company B: 8
Company C: 7
Company D: 8
Company E: 10
Company F: 5
Company G: 10
Company H: 10
Picture 3: Lira and hobbits head for the copse
The copse is up a fourth hill which the party passed on their right. It is the hill to the east, the one way that they have free, especially because most of the damage has been done to the enemy against the companies that were closest to the rear of the party.
Their numbers severely depleted toward the rear of the party, Companies B & C shift toward the rear.
Lira, Gorby, and Anson run for the copse. While Lira is doing this, she kills 2 more of Company B. Lumiel kills 2 more of Company B. Falowik kills 1 more of Company C. Thoronmir kills 3 of Company C. Finéwen kills 2 more of Company D. Eswen takes out 2 more of Company F.
Company E starts by shifting around to where it looks like most reinforcements are needed, which is by Lumiel and Lira, but on their way around they see Lira and the hobbits running for the far hill, and all ten give chase - but they've taken the long way around and do not catch up until the three have made it into the copse.
Company B: 4
Company C: 3
Company D: 6
Company E: 10
Company F: 3
Company G: 10
Company H: 10
Picture 4: The main group move toward the copse to rejoin Lira and the hobbits.
Lira kills 3 of Company E with bow and arrow. Thoronmir kills 3 more of Company D. Falowik kills 1 more of Company C. Lumiel kills 2 of Company B. Eswen finishes off Company F & B with bow and arrow. Finéwen kills 2 more of Company D.
Company B: gone
Company C: 2
Company D: 3
Company E: 7
Company F: 1
Company G: 10
Company H: 10
At this point the leader releases his two companies held in reserve (he waited way too long). Thoronmir calls for a retreat to the copse. Thoronmir is joined by Lumiel and Eswen, and Finéwen follows close behind. Falowik picks up Uien and follows the others. Falco is forgotten about, left among the horses and ponies; it is dark and he decides to stay hidden in the dark among the horses.
While they gallop up the hill, various of the party dispatch what is left of Companies C & D & F, and even manage to take out 3 of Company G. Thoronmir blasts through Company E, taking out one more of them, and everybody but Falco is within the protection of the trees, although Thoronmir's horse falls on him.
Company E: 6
Company G: 7
Company H: 10
Leader: 1
Enemy killed: 57. Left standing: 24. The party still numbers 10, and 3 of them are wounded. The remaining 7 have taken not even a scratch.
Here's the upshot. We're tougher (and luckier) than we think.

Now that we're among the trees, it will be even harder for the enemy to take us out; and Elven night vision will make the enemy easy pickings with bow and arrow. Yes, they have us surrounded (except for Falco), but the only way they can extricate us is to burn the copse down. They haven't thought of that yet, but it may not take long.
So, here's what I need from you guys: each of you please edit your most recent posts to take into account the fact that the force arrayed against us has been almost completely depleted, and they are likely to be severely demoralized.