Do keep in mind that they're a registered charity, a not-for-profit.

The reason I mention this is that "even though it would net them a lot more money" means that by doing it in the UK it isn't hurting shareholders, but the charity's goals - as mentioned in the blog itself.

I don't know whether it would be better to have £x more profit for the charity or to make y more boards in the UK, but either way you have to assume they're doing what they think is best as a charity.