Why native species? There are many conservation bodies in the UK specifically geared to protecting native wildlife, in fact this country has laws protecting wildlife which are well upheld compared to other countries which have other priorities and issues. I don't think it is a useful role of UK zoos to prioritise native wildlife conservation although there is a great contribution to be made by them.
The Giant Panda example is different from doing some zoo outreach in Eastern Europe. China can afford to conserve its Pandas, it doesn't need the west, and Western zoos are net consumers not producers of giant pandas, so it is a bogus conservation species in our zoos.
If YWP spent £200,000 on 'lions of the serengeti', with huge glass viewing galleries, vantage points and fancy interp for some Safari park-bred common or garden African lions, would anyone be criticising them?
So Lions are in their collection plan, they decided to do some outreach via fundraising, it will be good experience to pave the way for rarer species....they won't be breeding from them, whats not to like?