Dunno if my LBS is shite or what but...

The BB cups were not tightening up properly so they cut out a small section of the lug and rewelded it. They then re-taped the thread, which was not aligned straight as when you tighten the cups up the axle spins as if bent. I have tried various axles.
Anyway the last time i got the bike back with all the cups tightened right up but now the crank has bent, and the whole assembly is creaking.
Why would the axle become bent from normal use. I have done 400 miles on it.
I think the cups are still out of line.

BB cups not tightening.. cut lug? Do not understand. The axle shouldn't bend (unless it's particularly cheesy) are you sure the cranks/bb are actually installed straight? Could the chainring be bent? What are you eyeballing that gives you the impression of bent?