Thanks for your question.
If you have doubts about the legality of the Will because either it was incorrectly executed or your brother put pressure (undue influence) on your mother to make/sign the will then you have to see a contentious probate solicitor.
He will also be able to deal with the withdrawal of monies from your mother's account,
If after taking your specific advice the solicitor consider that there are grounds for opposing the administration of the estate then they will enter a caveat against the estate. This prevent a grant of probate being issued in the estate so that your mother's assets cannot be dealt with by her executors. It costs £15 and lasts for 6 months.
Your solicitor will correspond with your brother (or his solicitors) with a view to making sure that your mother's estate is not administered in accordance with an illegal will.
You can find solicitors in your area using the following Law Society search engine:-http://www.lawsociety.org.uk/choosingandusing/findasolicitor.law
Enter your postcode and select "wills and probate".
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Edited by Thomas on 10/31/2010 at 9:11 AM EST