You will need to get a Grant of Probate unless your mother had already nominated a trustee before she died ( in her will).See
http://www.courtservice.gov.uk/cms/wills.htm.I did this for my father in law's estate. It's a fairly simple proceedure of form filling and a quick visit to the Probate Office in your nearest town/city.You don't need a solicitor.The present Inheritance Tax threshold is �263,000 (for a death between 6 April 2003 and 5 April 2004 the threshold was �255,000). Very broadly, if the net value of the assets owned by deceased, together with
their share of any assets owned jointly,
any assets held in trust from which they had the right to benefit,
any assets they had given away in the 7 years before they died, and
any assets which they had given to someone else, but in which they retained an interest or benefit
does not exceed this figure, there should be no Inheritance Tax to pay as a result of the death. Where the tax threshold is exceeded, you will have to pay at least some of the inheritance tax that is due before you can get a grant.