The Board has already reached out to these projects by asking if the newsletter could be translated into these languages. My suggestion is we set aside two reserved seats on the Board for people who actively contribute to at lease one wikimedia project in a minority language of the UK.
Two seats is too many, especially if the board is only 5 members (if it is increased to 7, it's a little more reasonable) - the proportion of members from minority languages is likely to be much less than 40%, and the board should not be so grossly disproportionate. One seat is worth considering. There are ways of giving minority languages an involvement in running the chapter without them being given a dedicated board seat, though - a system of committees (possibly with budgets and delegated powers - we need legal advice there) could work, there is also the possibility of a more complicated system involving subsidiary companies, but that's too complicated to worry about now (I'm not sure if there would be any real benefits - perhaps it's an idea best discussed over a pint after the AGM).