I did up a standard letter on my pc, and changed the address and ref number for each utility, insurances (car, travel, life etc), bank account etc. Meant I could easily keep copy of each.
Separate letter to house insurance as you're cancelling 1 and starting a new one.
BOx with full roll kitchen towel, spray cleaner, bleach, wash up liquid, pot scourer, tea, coffee, sugar (even if you don't use it, some helpers may), plenty biscuits, mugs, glasses (for water), a pot or kettle, couple of screwdrivers, bin nags, etc. Goes with the first person into new house. (You may want similar as last box out of old).