This is where my quote came from
http://www.hmcourts-s...te/why_will.htm#chart
If you have everything in joint names then your wife will inherit (but it will take time to go through the legal process if there is no will)
If there are assets in your name only then she may not get them all - it depends on how much your estate is worth.
A will is well worth the money it costs to make (Probably in the region of £100/£150) and, in my opinion, it is worth going through a solicitor to make sure it is exactly what you want.