I wrote this song back in 1993, and I must say I am flattered (and somewhat shocked) by the amount of interest shown in this forum !! You can find the original lyrics at http://www.sydmeats.co.uk/lyrics/prawns.htm
I am delighted to hear that so many people are performing it, but please note the copyright details which are given at the address above.
I will make a copy of the tune available via my web site (watch this space for details). I won't promise any timescales, but hopefully it will be within the next few weeks.