I'm not conflating avoidance and evasion (although it's a fairly fuzzy line between them at times, and things which were once avoidance have been deemed illegal

I'm not conflating avoidance and evasion (although it's a fairly fuzzy line between them at times, and things which were once avoidance have been deemed illegal schemes after the fact on many occasions). Unsurprisingly I don't have obvious evidence of the UK government breaking UK law. However what I would suggest as evidence of ambivalence is the fact that several jurisdictions which are considered friendly to tax evasion and avoidance (so called "noncooperative tax jurisdictions") are UK dependencies. The UK could, if it really wanted to, crack down on the tax and company formation regimes in these locations, but they choose not to. That, to me, is evidence of ambivalence.