I think a lot of people on here don't actually understand how election campaigns work...
The Labour Party (and every other political party at the same time) were literally sending out emails saying 'if you want us to win this election, send us money'. They were begging for donations because election campaigns are expensive. People donated to the Labour Party, or any other party because they want to support their ability to win that election.
Rich people who also want Labour to win the election can equally choose to donate, just like me or any other person on the Labour Party mailing list. And some supporters chose to support the election campaign with different kinds of help - clothes or a quiet house away from the press (which is recorded with a notional value assigned just like any other 'donation' would be).
Honestly, I'm really not sure how anyone can get themselves worked up about this, unless of course you're just anti Labour and being extremely disingenuous (much like the daily mail).
The only thing Labour are guilty of on this subject is appalling PR management of the story!