The campaigns of the two major parties will come out at around 15-20 million apiece.
The source of the dosh is:
1) 'Short Money' Public funds paid to parties
2) Donations from rich people who either a) believe in the party or b) know a winner when they see one
3) Subscriptions from members (like me)
4) Bank loans, because nobody wishes to lose for a crappy five million or so.
There are statutory limits, but it is too boring to look them up.
At the risk of sounding really boring, the UK probably has the most honest political system in Europe.
French Presidents under investigation.
German ex Chancellor ditto
Italy - well, what can I say?
the list goes on......