"Firearms Act 1968 [as amended by 1997 act] - Section 30A Revocation of firearm certificates
(1) A firearm certificate may be revoked by the chief officer of police for the area in which the holder resides on any of the grounds mentioned in subsections (2) to (5) below.
(2) The certificate may be revoked if the chief officer of police has reason to believe—
(a) that the holder is of intemperate habits or unsound mind or is otherwise unfitted to be entrusted with a firearm; or
(b) that the holder can no longer be permitted to have the firearm or ammunition to which the certificate relates in his possession without danger to the public safety or to the peace.
(3) The certificate may be revoked if the chief officer of police is satisfied that the holder is prohibited by this Act from possessing a firearm to which section 1 of this Act applies.
(4) The certificate may be revoked if the chief officer of police is satisfied that the holder no longer has a good reason for having in his possession, or for purchasing or acquiring, the firearm or ammunition which he is authorised by virtue of the certificate to have in his possession or to purchase or acquire.
(5) A firearm certificate may be revoked if the holder fails to comply with a notice under section 29(1) of this Act requiring him to deliver up the certificate."
You have a [limited] right of appeal under the same act.
"(6)A person aggrieved by the revocation of a certificate under subsection (2), (3) or (4) of this section may in accordance with section 44 of this Act appeal against the revocation."
"44 Appeals against police decisions
(1) An appeal against a decision of a chief officer of police under section 28A, 29, 30A, 30B, 30C, 34, 36, 37 or 38 of this Act lies—
(a) in England and Wales, to the Crown Court; and
(b) in Scotland, to the sheriff.
(2) An appeal shall be determined on the merits (and not by way of review).
(3) The court or sheriff hearing an appeal may consider any evidence or other matter, whether or not it was available when the decision of the chief officer was taken.
(4) In relation to an appeal specified in the first column of Part I of Schedule 5 to this Act, the third column shows the sheriff having jurisdiction to entertain the appeal.
(5) In Schedule 5 to this Act—
(a) Part II shall have effect in relation to appeals to the Crown Court; and
(b) Part III shall have effect in relation to appeals to the sheriff.”
Without knowledge of events or of special circumstances, it sounds like a dubious decision, one open to appeal.
As a final resort you could have any weapons with sentimental value made 'safe' in order that you could keep them, as they would then fall outside the law.