The berserker lord on badger is on a standard 2550 cav base. The king on large beast is on 5050.
The model pictured is effectively the unique character sveri - who is a large cav model (but can easily be fitted on a cav base - think an earlier version of the model came with one)
The Berserker Lord on brock is on a Cav Base (25×50mm). Mantic doesn’t sell a specific model, bit u can use a spare brock rider. The pic shows Sveri Egilax in Hellbrock, a “Living Legend” from the Free Dwarfs list. (The Model could also be used as a Dwarf Lord on a Large Beast with a 50x50mm base).