When interpreting statute, it is generally useful to start with what the statute actually says. Sections must be read as a whole, and I would say that the same would apply to paragraphs.
(3) Subject to sub-paragraphs (4) to (6), the red signal conveys the prohibition that vehicular traffic must not proceed beyond the stop line.
(4) Sub-paragraph (5) applies on an occasion where a vehicle is being used for at least one of the purposes set out in sub-paragraph (6) and the observance of the prohibition in sub-paragraph (3) would be likely to hinder the use of the vehicle for that purpose.
(5) The prohibition conveyed is that the vehicle must not proceed beyond the stop line in such a manner or at such a time as to be likely to endanger any person or to cause the driver of another vehicle to change its speed or course in order to avoid an accident.
(6) The purposes are—
(a)fire and rescue authority;
(b)Scottish Fire and Rescue Service;
(c)ambulance;
(d)blood service;
(e)providing a response to an emergency at the request of an NHS ambulance service;
(f)bomb or explosive disposal;
(g)special forces
(h)police; and
(i)National Crime Agency.
It seems pretty clear that the "the vehicle" mentioned in sub-para (5) is a vehicle being used for one of the purposes in sub-para (6). In your example, it is the ambulance that can jump the red light as long as it does it carefully, not the car that is blocking its path.
Case law tells us that an on-call ambulance driver cannot rely on the speed limit exemption for ambulance purposes to drive to the depot to pick up an ambulance to use for ambulance purposes, so, before you ask, no, getting out of te way of an ambulance is not going to constitute use for ambulance purposes.
If there is a risk of death or serious injury if the ambulance (or other vehicle being used for sub-para (6) purposes), is blocked until the lights change, then the defence of duress of circumstances might apply, but unlike jurisdictions with a broader defence of necessity, crossing the line simply because it is the lesser of two evils is not a defence. Whether it would be in the public interest to prosecute is another matter, as is whether a court would find special reasons not to endorse.
