Historically, economic crashes are followed by periods of faster economic growth, so asset values may bounce back. If so, planning now grants numerous benefits.
Capital Gains Tax will be lower. Family trusts are limited by a tax free cap of £325,000/person (a couple can establish a trust with £650,000). With asset values depressed, more can be transferred into a trust tax free. Larger gifts to family members are possible, and the value at the time of gift may be subject to Inheritance Tax if you die within seven years, but future growth is tax free.
Now may also be a time when children or grandchildren are most in need of financial support. If you can afford to give assets away, this may be your best chance to do so.