Clearly, to do all of the units involved at Medina de Rio Seco would involve a substantial lottery win and a very big room to game it in. Neither of these is applicable at the moment, so I'll have to make do with creating a representative selection of troops.

My interpretation of the OOB for Medina is as follows (I've gone mostly with the Partridge and Oliver version). I have also commented on the availability of figures.

Part 1 - The French

Imperial Guard - nobody makes any of these in 40mm!
Fusilier Chasseurs - 2Battalions
Fusilier Grenadiers - 2 Battalions

1 Squadron each of
Chasseurs
Chevau-legers
Dragoons
Gendarmes (Oliver and Partridge suggest that the Guard Cavalry was only Gendarmes)

10 Guns

Merle's Division
47 Line - 2 Battalions (some sources suggest 1 Battalion)
2/3rd Swiss - 1 Battalion
14 Provisional Line - 1 Battalion
86 Line - 2 elite companies
13 Provisional Line - 4 Battalions
17 Provisional Line - 4 Battalions
18 Provisional Line - 1 Battalion

12 Guns

Mouton's Division
4 Leger - 3 Battalions (Leger not made in 40mm)
15 Line - 2 Battalions

6 Guns

Lasalle's Brigade (nobody makes a Lasalle figure in 40mm, which is a shame)
10 Chasseurs a Cheval
22 Chasseurs a Cheval

So some real issues here. Nobody makes the Guard at all in 40mm (Sash and Saber does Guard Grenadiers a Cheval, which could double up as Gendarmes at a pinch).

Nobody makes figures for Leger in 40mm, which could be just a paint job to make do, but I would rather have specific figures, there are some uniform differences from the Line.

A Lasalle personality figure would be great, as would a Bessieres.

The question is, how to get around the lack of availability of some key troop types.

Sash and Saber 40mm Napoleonic French Officer. Lots of bits come with this model, so there's plenty of scope for conversion - more Spanish Officers for sure. 

15th Line in the 1806 uniform. Still have a couple of companies to do, they've been on the painting table for quite a while. 

The major malfunction when painting these was that I forgot to scrape off the number from the shako plates. The figures are mostly from the regiment pack of the 57th line and so they have this on the shako plate.

When I do the 2nd battalion, I'll remember this. It's a minor point, but I know it is there and it will bug me. It's one of those moments where you've just finished basing everything, have a closer look and think, bollocks!

This unit is inspired by the picture to the right. 

Sash and Saber 40mm French Napoleonic Officer converted to a Spanish Officer. Just a matter of scraping off the lapels, adding a dollop of greenstuff for new lapels and cuff flaps, and using a punch to make the buttons. For the plume, drilled a small hole, added a very short length of wire, built it up with greenstuff and there we go.

Perry Miniatures 40mm Spanish Infantry. I painted these some time ago as Provincial Militia. Whether any of the Provincial Militia at Medina actually wore the white uniform is up for discussion. However, they are done now so in white they will stay!

40mm Sash and Saber Napoleonic French Infantry Battalion. 36 Figures.

My intention is to use these as the 47th Line.

My overall aim is to try and recreate some of the forces at the Battle of Medina de Rioseco , 14 July 1808. Some of them will be fairly straightforward as figures already exist. Some will prove to be difficult, involving considerable conversion. Some will mean the creation of new figures.

I am doing this in 40mm as age and eyesight makes anything up to 28mm quite difficult. The downsides to 40mm are 1. the cost and 2. they are larger so will take longer.