Brave Sah, I hope you are truly a Robin, as that is the guild of my family!
I love the song of Camelot.. - I - have - to - push - the - pram-a-looooot!

As far as faction choice is concerned, I always pick the harder challenges in all aspects and dilemmas of my life, it is my custom, and that leads me to do the same whenever I play this game.
Not only for my asceticism, but also for my greater comfort with small beginnings - I do not like being thrown into the government of a great empire.

Thank you for your advice on archers - I have not yet played a game where my archers were less than 3 ranks deep!
Yes, this is a product of the Rome: Total War doctrine, in which archers could be in column formation and still loose with great effect.

Corleone, I had not used any Men-At-Arms, for I found them to be very weak in a previous campaign as the Castilian faction - however I feel this is because I probably asked to much of them, and expected them to be the spearman and the swordsman.
I will try them in the way you have mentioned.

As for archers, I had lost faith in them because they did not seem to be effective in mounting casualties, I had one unit loose it's entire ammunition supply and have caused ten deaths.
However, as you have seen, this is because of the ranks in which I deployed them, and I will now use archers with greater ability thanks to Sir Robin.

I did perch my men atop a hill - admittedly it was the smallest hill, however it was also the steepest hill, and the closest to the enemy, meaning I was immediately able to loose arrows amongst them, and pressure the Muslims into attacking immediately up a steep advance.

As for the confusion about my formation, don't allow my diagram to fool you, the forum font setting shattered it.
I had my sergeants formed in a Roman Manipular position, as I intended to charge the enemy when they were climbing the sharpest ascent of my hill.

This allowed two gaps on either side, on the right I placed the King and two units of spearmen to flank and drive away cavalry.
The other side housed my archers perfectly, but ineffectively because they were ranked in 4 lines each.
Now, here is the main confusion;
halfway down the eminence, at the place where the ascent is steepest and most difficult, at the point where I intended my infantry to hit the enemy - I placed in hiding two units of Royal Knights - to deliver a heavy charge and then retreat, and three units of Urban Militia to cut apart the back of the enemy.

This failed because the flanking units were outnumbered by the amount of enemy companies still attempting to catch up to the front line which was fighting the Sergeants.

I know realise about all the units you have mentioned however, and I have learnt harshly that both Almohad Urban Militia and Danish Viking units are champions of all battlefields - and cheap!

I found that the Scottish armies are far more suited to my fighting style.
I am still fighting a rather interesting campaign, in which I was going to make Scotland a peaceful, yet powerful trading kingdom that kept peace with England and conquered Ireland and Scandinavia.
However my paranoia went insane when England starting massing troops in Northumbria, and the army of 8 Clansmen and 4 Royal Knights (Including King Malcolm II), suddenly declared war on England and attacked Northumbria.

I was outnumbered 2:1, however by using the speed of my infantry to cut around the English militia and gain their target mountain, I charged them down a great descent, and by shock and bravery - routing the four weakest units with sly discrimination - the entire army only withstood the attack for fifteen seconds, and Prince William III was killed.

Though this petrified the English of my army, my most expected peril occurred, a counter attack was launched on the homeland, and I lost Edinborough to King William the Conqueror.
So I used that same tactic mentioned, and raided every English province, Mercia, Wessex, Wales and Northumbria again.
They would take back a province because I had left it, and within two turns I would of shocked them out of the province.

With my army of 760 men I killed over 3000 English, and took around 1300 prisoner, including King Alfred II, (William II was killed in action by King Malcolm III), every province I took, I destroyed every piece of infrastructure.

I used a cheat to see how this affected England on the continent, and saw that France owned all provinces except Normandie - though they never declared war!
Due to the havoc at home, England had lost over 9 Provinces to rebellion, and now King Alfred II and an army of 395 men sleep under the stars in Mercia with a bare income.

Meanwhile Malcolm III is back in Scotland in command of Edinborough, with a treasury of 25,000 from the constant raids and ransoms, and developing Scotland in total privacy and security!!

The year is 1107.

I found my preference it seems!