Do you guys have national debates in the American sense, or does the Prime Minister's Questions have to suffice?
None of the party leaders really want a debate (although there's sometimes a semi-serious challenge for one) so no... we don't have one.
PMQ's doesn't really suffice because it's really just a pantomime for political obsessives and journalists and lost it's real purpose (ie: to question the P.M) during the bitterness of the '80's.
We did nearly have a debate in 79 though... Callaghan challanged Thatcher to one and she were only stopped accepting by her advisors. Pity... Callaghan (one of the best debaters in post-war politics) would have demolished her.