My Vespa Sprint Veloce has just started pouring fuel out of the carb

I've had the carb off tonight, taken everything apart and blown through with carb cleaner but still leaking like a sieve
The carb is a Dellorto 20/20 and the fuel is coming out of the overflow /breather by the banjo. The float doesn't appear to be punctured but I'm not sure about the needle. It may have a slight ridge in it but its hard to tell because they are so tiny.I've tried swopping with another float needle but still leaking. Then again that needle wasnt known to be a good one... There is definitely no crud in the tube that the needles sits in
Am I on the right lines here or should I be looking for something else. I'm going to try and get another float and needle from Barnsley parts fair tomorrow just to rule that out as the problem
Annoying, because I was looking forward to a sunny ride over to Barnsley tomorrow.