Good news, UK acolite, this board has many members that know a great deal about Ludwig (I am not in their league, but, I have a few Ludwig kits).
This is what I know...
1960-68 keystone badges 3ply mahogany/poplar/mahogany shells with reinforcement rings. Clear inside finish '60-61, white paint '61-68 (there will be exceptions) It's my opinion, this time frame is the "Ludwig" sound that everyone wants. The drums are pricey, but, worth it. Try to get a beat up kit, to restore. You will find the original parts on ebay and online.
Blue and Olive badge-1969-'83?-3 ply shells maple/poplar/maple (sometimes mahogany was still used) rerings- interior granitine paint up to '76
Classic series 6ply maple and poplar with no reinforcement rings, clear internal finish. This is when the sound changes (my opinion). Still great, just different. Use this site for the badge/serial number timeline.
In this time frame you have the Ludwig Standard, which is the same shells, just cheaper hardware. You can get this kit at cheaper prices, but, with the great Ludwig sound. Different badge..A rounded triangle with standard in black.
Black and white badges-Rocker I (my kit in the picture) 4ply maple, clear internal finish, high end Classic lugs, no reinforcement rings.. Rocker II-same shells with a brown speckled Ludcote finish, lower end Standard lugs. The prices are much lower. If you can find a Rocker I kit, for around $150- $200 that's a nice find. I have this kit and it sounds good, it just does not have that classic Ludwig sound, but, with head selection I can get it pretty close.
The picture I am supplying is my '83 Ludwig Rocker (my first kit). This kit had the black and white badges (I still have them), but, when I rewrapped the set, the badges were shot, so, I put blue and olive badges. I rewrapped in the 60's style black oyster pearl (the original was blue cortex, very cheap looking). I have owned 60's keystone kits (2 of them and they sounded the best, should not have sold them), Vistalites (I still have my Bonham, sounds great), the Rocker (sounds good with proper heads and tuning), and a 2006 Ludwig, which I did not like and sold right away at a break even price (the person I sold the kit to, LOVES THEM and thinks I'm nuts).
The good deals (in my opinion)
Early 70's, blue and olive badges, 3 ply shells with the reinforcement rings
late 60's-early 70's Ludwig Standard