Have a look at my new spoke length calculator web app!

I used an on-one hub which is in the database, plus i also measured with Verniers to double check?

Did you measure your rim's ERD to check too - it's possible they vary a bit as the dies they are extruded from wear out & are then replaced.

Could have been to do with the nipples i used, although they are just standard "short" nipples that came with the spokes?

I think spokecalc & edd's calculations assume normal short 12mm nipples, so probably not.