The WHO, unfortunately, are beholden to political influence and therefore are basically a complete irrelevance in this discussion. It's like the Pope calling for peace during a World War - all very nice to do, but actual reality gets in the way.
The UK government will, correctly, emphasise the vaccination of their own populace, like any country would do. Charity begins at home. I'm sure we'll be supplying massive amounts when we have excess.
On another note, 600k vaccines in one day - staggering achievement. Four weeks ago I was expecting that to be around the weekly amount at best given the Tory track record.