I can certainly second the Fogou stuff as being quite Oldhammer inspired, but alas not cheap. Depending on exactly what period you are after you can get hold of a lot of the Citadel "hard foam" range second hand on ebay, but you do have to be patient to get things at acceptable prices. They were never really pre-painted but did have a quick and dirty black/white spray and some flock to make them usable "out of the box".
I would imagine there are probably scans of the old Citadel card buildings floating about on the Internet that you could be naughty and acquire (obviously to avoid cutting up your originals you understand). That might be a quick way to generating some old feeling terrain. Buy some trees (K&M very good for the old bog brush trees got some not too long ago) and a bag of lichen and away you go!
Given most of it was original made "back in the day"
Scotia Grendel might tickle your fancy. Again you'd have to do the painting, but they have some classic bits and pieces in the collection oozing character, although with more of a dungeon target than open battlefield for the most part.
Whilst they probably don't have the rustic charm of hand made
Tabletop World do make stunning resin fantasy buildings. Their older pieces are all cast resin and they are starting to move into producing new pieces as 3D prints I believe. They are expensive, but very lovely buildings. You would of course have to paint them, but did I say how lovely they are?
If new GW isn't too laden with skulls of course GW are re-releasing some decent terrain pieces as part of their
Old World series. Prices have generally been better than we expected. The hills and walls are perfectly decent bits of generic terrain. Again you would need to paint.
My local gaming store has some pre-printed fantasy cardboard terrain from
Battlesystems which I always think looks like a good way to get an instant battlefield. They also have
some pre-painted MDF buildings which I've not seen elsewhere.
Deepcut now have some pre-painted terrain pieces, as does
UrbanMatz. As to how "oldhammer" some of that looks well... Alas nothing but handmade will really quite capture that feel and there probably isn't a large enough market out there to support too many companies. There are a million MDF flatpack kit makers, but the above links are probably as good as especially if you want pre-painted.
This
chap in Germany does pre-painted modular terrain. I have some of his older stuff, looks like he's moved onto hexes now and is possibly printing rather than casting pieces. I know he used to do modular rivers, but I don't know if he still does. Still might be worth a look to see what he is up to now.
As Sade said Battlefield in a Box are the other big maker, certainly their
rivers and so forth are pretty generic and I doubt you'll find anything better at the price.
Some others that you might want to look at (although you'll be needing those paintbrushes) for bits and pieces
- Tiny worlds some decent walls and scatter
- Alternative Armies scatter terrain
- Fenris Games Ian has some lovely pieces in his store and his newer rubble city might be of interest.
- Renedra do have some bits that work for Fantasy, but they do have more of a "I pinched this from my Dad's railway layout" look to them.
- Bad Squid Games have a lot of smaller bits of scatter in their current lineup if you want more dressing type pieces.
- Mini Monsters I like their resin terrain pieces, Zealot in the UK carry most of their stuff.
- MOM Miniatures often have interesting pieces, but I have found their casting to be a bit iffy in the past.
