Valuing shares and/or unit trusts

Beenie

I would like to know if there is a standard method of valuation of these investments following the settling of an Estate.

The pared down facts are these:

• Relly died and left unit trusts in Hargreaves Lansdowne.
  
• We already had an account with that company so, in correspondence with the executor, agreed to having our share of the legacy transferred into HL.
  
• The executor has not used the normal buy/sell prices, but has used something they term 'an appropriation value' which was not made clear to us at any time prior to the distribution. Had we known this, we would have had a straight payment of cash (as the Will provided for £xxxx, but we have received £xxxx less £400 due to the odd valuation by the executor).

Any ideas please?