The only way you could find out from official sources (apart from what has been said above) is if your mother requests a copy of the estate accounts, which she is entitled to do as a potential beneficiary under the intestacy of the deceased. Your mother (and only your mother) could request a copy of the accounts be delivered to the court by issuing a summons under s25 Administration of Estates Act 1925, or more expensively under Part 64 of the Civil Procedure Rules. You are not "interested" in the estate (since the deceased's mother survives) so you personally could not obtain a copy. This comes with the caveat that (generally speaking) the courts are unwilling to make an order in these terms if the estate is still under administration and less than a year since death has passed.
It is one of my gripes that probate is the largest financial industry there is and is largely unregulated. However, be aware that in large estate, the Capital Taxes Office and the District Valuer are likely to take a fairly keen interest.