This topic is of interest to me too – I would really love to have some dismounted cavalry for a skirmish game (for scenarios) and Wargames Foundry make some, but not enough for what I have in mind.
I have thought of doing 28mm, with 10 to 20 figures per side myself.
In addition to Empress (and Perry, but I am including a link for them anyway) mentioned above, these seem to the the options (I am sure there are more though).
I am guessing pikemen would be of little use for a skirmish, but musketeers, dragoons and cavalry would be ok.
I have looked at Perry Miniatures: https://www.perry-miniatures.com/index.php?cPath=23_40_45
Wargames Foundry have a reasonable range, with some that are very skirmish friendly: https://www.wargamesfoundry.com/collections/english-civil-war
Renegade make some nice looking figures (but postage to Australia isn’t the best compared to other companies): http://www.renegademiniatures.com/eng_civil.htm
Bicorn have a range you might like: http://www.bicorne.net/acatalog/English-Civil-War.html
Redoubt have some – not too many photos though: http://www.redoubtenterprises.com/shop/?page=shop/browse&category_id=26a547b25cea83d016c35e12db9cbbba
Dixon have what looks like a large range, but I would prefer to have photos available before ordering: http://www.dixon-minis.com/shop/english-civil-war/
Of course there are the plastic Warlord box sets too.
I did contemplate 15mm (and 10mm!) for a skirmish game, but they looked more at home in massed units that a skirmish game. I like the Muesum Minatures range, but they no longer sells indivudual figures, which means if you want one figure, you will have at least 5 spares lying around.