(Update so far)
So its now been in the hands of another mechanic (this ones a local garage and I've dealt with them before) and they're looking at the carbs and filters again - mostly because they were full of crud.
Excitingly (not) it turns out that the Triumph mechanic didn't put the needles back in the carbs and possibly damaged/didn't put back properly the float bowls.
So two weeks later new needles, filters and bits arrive. They re assemble and apparently it fires up fine. A little while later my carbs start leaking again!
They've had a look at the carbs and apparently the little brass 'seat' that the needles go into (or sit in) isn't holding them in properly. It looks worn apparently (ill see for myself tomorrow).
This is causing the leaking problem as the needles aren't sat doing their job properly (according to the guy).
Worse news - apparently I can't order in that part from triumph separately. They guy is hunting on eBay as we speak but it looks like my hopes of this being an easy fix are dashed.
Heck, I don't even know if that's the underlying problem (the breathing one) or just one of the many that developed when it was with the dealer!
Looks like I'm going to have to fix then get rid, I just dont have that kinda cash lying around.
Still, weather's nice!
