Your leave to remain and relevant entry clearance (visa, residence permit) are no longer valid once the Home Office decides to cancel your permission to stay (previously curtailment) and you leave the United Kingdom and Ireland.
Therefore, you should not attempt to use your British residence permit.
From the Immigration Rules:
20A. Leave to enter or remain in the United Kingdom will usually lapse on the holder going to a country or territory outside the common travel area. However, under article 13 of the Immigration (Leave to Enter and Remain) Order 2000 such leave will not lapse where it was given for a period exceeding six months or where it was conferred by means of an entry clearance (other than a visit visa). [...]
The exceptions (in the Order cited) for long-term permission to remain no longer apply to you once the Home Office cancels (curtails) your permission.
13.—(1) In this article “leave” means—
- (a) leave to enter the United Kingdom (including leave to enter
conferred by means of an entry clearance under article 2); and
- (b) leave to remain in the United Kingdom.
(2) Subject to paragraph
(3), where a person has leave which is in force and which was:
- (a)conferred by means of an entry clearance (other than a visit visa) under article 2; or
- (b)given by an immigration officer or the Secretary of State for a period exceeding six months,
such leave shall not lapse on his going to a country or territory
outside the common travel area.
(3) Paragraph (2) shall not apply:
- (a) where a limited leave has been varied by the Secretary of State; and
- (b) following the variation the period of leave remaining is six months or less
However, a Canadian visa or permanent resident card allows you to transit landside the UK without visa (but still subject to Covid rules) if your flight departing the UK is on the same calendar day as your date of arrival into UK, or on the following calendar day.
If you hold a Canadian visa or an entry document other than the PR card, including a PR visa or PR travel document, a landside transit is only allowed if you are travelling from/to Canada on a reasonable itinerary. There is no restriction on the destination or origin country if you have a PR card or if you transit is airside (i.e. you do not pass immigration control) but you still have to prove you are a genuine traveller in transit.