It seems you can keep current margin requirements if you are eligible as a professional client. This is the procedure taken from here:

https://www.handbook.fca.org.uk/handbook/COBS/3.pdf

Elective professional clients ......................................................................................................

A firm may treat a client other than a local public authority or municipality
as an elective professional client if it complies with (1) and (3) and, where
applicable, (2):

(1) the firm undertakes an adequate assessment of the expertise,
experience and knowledge of the client that gives reasonable
assurance, in light of the nature of the transactions or services
envisaged, that the client is capable of making his own investment
decisions and understanding the risks involved (the "qualitative
test");

(2) in relation to MiFID or equivalent third country business in the course
of that assessment, at least two of the following criteria are satisfied:
(a) the client has carried out transactions, in significant size, on the
relevant market at an average frequency of 10 per quarter over
the previous four quarters;
(b) the size of the client's financial instrument portfolio, defined as
including cash deposits and financial instruments, exceeds EUR
500,000;
(c) the client works or has worked in the financial sector for at least
one year in a professional position, which requires knowledge of
the transactions or services envisaged;
(the "quantitative test"); and

(3) the following procedure is followed:
(a) the client must state in writing to the firm that it wishes to be
treated as a professional client either generally or in respect of a
particular service or transaction or type of transaction or product;
(b) the firm must give the client a clear written warning of the
protections and investor compensation rights the client may lose;
and
(c) the client must state in writing, in a separate document from the
contract, that it is aware of the consequences of losing such
protections.