85* minutes.
You need to be there fifteen minutes before show time.
You need to allow about fifteen* minutes for the boat to get from MK to FW and to walk to the restaurant.
You need to allow about fifteen* minutes for a boat to arrive.
You need to allow about twenty* minutes for the bus to get from CSR to MK.
You need to allow twenty minutes in case you JUST missed the MK bus.
*Times approximate. Grab a copy of the Unofficial Guide - any of the last few years is sufficient - and use the 'from-to' time chart in the Guide's transportation section for exact times.