Based on what you wrote I contacted the dealers I usually buy from both online and at a store. They contacted their UK distributors and asked about ordering Boer Infantry in particular. They were all told Strelets have never sent re-stocks or informed them of re-stocks so they are classed as no longer in production.
Most stores use specific distributors in the UK or are part of larger chain of stores where a central office orders items.
If the sets are in continued production it might be a good idea for Strelets sales team to let UK distributors know what sets can be re-stocked.
I note two dealers in Europe say the same thing -no longer in production and, as far as the Boers go, I have found no sets online at all.