Well. That's what I did. (Well, mostly. I'll fess up to cheating very slightly later).
So the obvious army to pick is the "Men-at-Arms" which is basically a War of the Roses army -- and it turns out I have two boxes of Perry plastics with a couple of test figures assembled. Also nearby is a box of Gripping Beast dark age warriors.
So the warriors can make the peasant levy;
10 figures and a leader makes a 30p unit.
The various retinues will provide bows, bills and men-at-arms.
Two 80p units of bows. Each has 12 figures, leader and banner.
The bills are a 70p unit of 10 figures, leader, banner and musician.
The men-at-arms are the smallest constitute of each retinue, combined they're a 268p unit of 8 figures including a leader and banner.
That's clearly not enough shooting or fighting units, so we better hire some mercenaries.
12 crossbows for 80p...
...and 12 handgunners for 80p should add some shooting.
12 pike with leader and banner and musician for 66p will bulk out the fighting units.
Right, that's the army soldiers. Shooting units need resource markers to track their ammunition. There are tokens that come with FW, but they're fiddly and there's obvious opportunities there to make neater stuff.
This is where I started cheating a bit. First off, I bought some of the excellent casualty markers from Warbases. Then I wandered around a Partizan collecting bits and bobs. Some of the figures are the Perry metal pack of workers; the others are from Courteys/First Corps who make a fantastic dark age civilian pack. The barrels and other equipment are plastic Renedra, the brilliantly named "Dead Man's Baggage" pack and several sets from Warfare Miniatures. The pack horses are Redoubt. Mixed together, dry-brushed, washed and based up on the casualty markers they make much more atmospheric supply counters.
Then we need some leaders. We'll stick with foot versions to keep the costs down.
A war chief and two battle leaders adds up to 246p.
The battle leaders are a Joan d'Arc (give-away with Warhammer Historical's Age of Chivalry), and "Martin Schwartz" (a Partizan give-away). The war chief is (I think) a figure from Colonel Bill's Dark Age heroes range. These were all in the store of unpainted figures.
I also built a couple of extra bits for the army; the chap at the back is the paymaster (Perry figure and Warfare extras) and the encampment is from the First Corps pack. The blacksmith at the very back is another Partizan give-away figure from several years ago. He's slightly out of era, but never mind.
So that was quite an interesting project. I'm just waiting for their opponents to be painted to try them out...