Went down to the local mechanic guy and he showed me the part (which he's removed without damaging the carb itself).

Basically it appears that one of those 'sleeves' was significantly lower than the other one and that was causing things not to sit properly.

He told me he had put everything together with new needles etc (man i'm still annoyed that the last guy didn't have the sense to put it back together properly) and it fired up fine and seemed to run quite well until after a small amount of time the carb started flooding again (thats when he discovered the discrepancy).

So now it appears i have to buy new/second hand carbs _or_ somehow find that particular part - anyone got any experience with that bit? if Triumph don't do them do you reckon it's possible to get them direct from Mikuni?

Images of the part can be found :
http://picasaweb.google.com/JesterMinute/TheBike?feat=directlink

or

<table style="width:194px;"><tr><td align="center" style="height:194px;background:url(http://picasaweb.google.com/s/c/transparent_album_background.gif) no-repeat left"><a href="http://picasaweb.google.com/JesterMinute/TheBike?feat=embedwebsite"><img src="http://lh6.ggpht.com/_gt4f2uCNUjI/SZwjMuHA7TE/AAAAAAAAAVc/5f2xCV2_zoc/s160-c/TheBike.jpg" width="160" height="160" style="margin:1px 0 0 4px;"></a></td></tr><tr><td style="text-align:center;font-family:arial,sans-serif;font-size:11px"><a href="http://picasaweb.google.com/JesterMinute/TheBike?feat=embedwebsite" style="color:#4D4D4D;font-weight:bold;text-decoration:none;">The Bike</a></td></tr></table>

fingers crossed!