It was an offence under s105 of the Road Vehicles (Construction and Use) Regulations 1986 to open the door so as to injure or endanger a cyclist:
"105. No person shall open, or cause or permit to be opened, any door of a vehicle on a road so as to injure or endanger any person."
The question will be whether the opening of the door caused the accident or whether you were riding too fast and that caused it. Cycling up the inside has been going on for more than a century without legal objection so can be considered to be allowable. However you need to do it with care such that the passenger would have the opportunity to see you if they checked. It sounds from the damage to the door and the bike as if that may not have been the case and it may not have been reasonable for the passenger to have been able to see you before they opened the door even if they checked very carefully. Only you can answer that.
"105. No person shall open, or cause or permit to be opened, any door of a vehicle on a road so as to injure or endanger any person."
The question will be whether the opening of the door caused the accident or whether you were riding too fast and that caused it. Cycling up the inside has been going on for more than a century without legal objection so can be considered to be allowable. However you need to do it with care such that the passenger would have the opportunity to see you if they checked. It sounds from the damage to the door and the bike as if that may not have been the case and it may not have been reasonable for the passenger to have been able to see you before they opened the door even if they checked very carefully. Only you can answer that.