A one-to-one could certainly be more informative, but wouldn't get the audience - most folk would only watch whoever the big two happened to be.

For leaders debates, I'm in favour of including all the leaders - definitely including the Northern Irish leaders. Yes, I'm sure it would get a bit unwieldy, but I understand it's been done in other countries, and lack of exposure to the politics of other parts of the UK is one reason why the K is not very U!

Agreed on UKIP; I wouldn't include them as of now, because my criterion for inclusion of a party's leader would be the party having at least one current seat in the Parliament being elected. Unfortunately - in my view - that would also exclude the Scottish Greens, but there has to be a cut-off point somewhere and I think that one's both reasonably inclusive and defensible.