Part 2 separately, based on the Times annual degree results service, stopped some years ago. There is no common distribution. Some degrees were able to reach a 40-40-10-10% rough split from a first downwards, to some, like my own in law where there were no firsts for 8 years, and it went roughly 10-60-20-10, no one failed to my knowledge, the last figure was for a 'pass' degree where not enough subjects were passed for honours.
The 'tougher' technical subjects like engineering always got lower average grades than some of the more descriptive and philosophical ones, and before the union, Polytechnics tended to get lower averages (based on my own, the rest weren't published) than the Universities. So if you really want a 2-1, try an unpopular 'old' university with a fairly fringe subject like film studies or sociology. I'm not being elitist, as an ex-teacher I had to give advice to 6th formers so I needed to read up on marks versus employability. I hope this helps.