If I added up how much I owe and went bankrupt now will I be ok? - discharged within a year?
You might be OK, but your creditors won't be.
How much effort will the inland revenue be making to look for me?
Impossible to say. It depends on what you have (or haven't) done and how determined particular HMRC employees are to find you.
What is the likelihood I have a warrant out for my arrest? I am very worried about going on holiday as I don't want to get pulled up at the airport.
There has to be debt and default before arrest is possible. So unless someone has court judgements against you arrest is unlikely.
If you want to be able to sleep at night engage an accountant who is experienced in this sort of thing and then contact HMRC and tell them all they need to know. And pay what you can. Sorry to sound moralistic, but I am a fully paid up member of the "I pay my tax so I don't see why you should get away with not paying yours" club.