As you're in receipt of Higher Rate Care of DLA you are according to the WFI Regulations exempt.
The Social Security (Incapacity Benefit Work-focused Interviews) Regulations 2008
Section 3 Relevant claimant
(5) The fourth condition is that, on the day on which the requirement to take part in a work- focused interview would have arisen, the person is not treated as incapable of work in accordance with regulation 10 of the Social Security (Incapacity for Work) (General) Regulations 1995(d) (certain persons with a severe condition to be treated as incapable of work).
It may be worth contacting the office that deals with your IB and advise the that according to the regulations (quote them if you like) you are exempt from taking part in an IB WFI.
Just an aside. Please could you not type in upper case (all CAPITALS) as it makes it difficult for members using screen readers to use and also in forum parlance it amounts to shouting.
Thank you.
Nothing on this board constitutes legal advice - always consult a professional about specific problems