The Good Will Guide. 
This is very helpful information from the Catholic Children’s Society because it really does make a potentially very complex process quite simple. The asset and liability calculator is particularly useful. It should be read in conjunction with CCS’s guide to making a will (scroll to the bottom of the page), which covers the practicalities of will-making and includes a glossary of terms.

How to make or change a will.
This helpful leaflet includes a glossary of legal terms.