Hi,
Just had exactly the same thing in my 500 mile Tourance. I have Ultra-sh*t in and expected to pull out the nail see a little pink blob pop out and all be well !! ( just like on the BMF stand demo) No chance , air p*ssed out and I suffered serious ammounts of flattage.
I shoved a can of temp tyre weld stuff IN and went home . I then repaired the tyre with the B*W tyre plug thingies a week later, which is scary , jamming a 4" spike into the carcass etc.
I have done a few hundred miles since including a quick thrash from Bolton to the BMF and back and all is well although the valve got a bit sticky which led to a very slow leak when the cap was off ( due to paranoia )
I am fairly happy & confident in the plug repairs even though I was turned away at a couple of tyre fitters.
My nail was bang in the cente of the tyre so you have to make your own choice.
Good luck,
In retrospect I should have pulled the nail and gunned it for a couple of miles for the Ultra-s*it to do its centrefugal thing but the garage was on a dual carriage way so I didn't want to risk running flat to the rim.