A cunning amalgamation of the words 'lashy' - meaning alcohol-fuelled, and 'bants', which is short for banter. If one is planning a night (or even day!!) out on the sauce which is going to be ruddy good fun, then it is easier, and much, much cooler to say 'lashybants'. If the occasion is particularly significant, the term 'massivelashybants' has been known to have been used.
Wedders: Bizzle, how do? Any plans for this weekend?
Bizzle: Lashybants at The Church! Game?
Wedders: A megabus ticket and £200 cash says that I am!
Bizzle: Great news!