In a pre-record for GMTV on Sunday, a Plaid Cymru MP - Adam Price - has said there is "no veto" on coalition with the Tories. That's an understatement. The nationalists will be praying for an hung parliament so they (plus some Ulster MPs) can jump into bed with the Tories.
The Welsh and Scottish nationalists act as one party in Westminster today, and there will be more of them after the election. Only the Tories share their agenda: to move towards a Englishness agenda where Scots and Welsh MPs can't decide on uni tuition fees, foundation hospitals etc. Labour may share their lefty principles, but has far less incentive to proceed with granting more powers to all countries of the UK.