I think we are all getting a little too far over complicated here with suggestions.
Lets go back to basics and look at this logically without spending any money first.....
. Lets not worry too much about the Selespeed system just yet... something tells me that it will sort itself out once the engine has fired up and ticking over nicely
When you pulled over for the Fire engine to pass, did you mount a kerb?
Is the car currently standing at an angle, on the flat or incline/decline?
This can tell us a lot like position of the fuel pump in relation to the car or a sudden jolt making the battery or earth cables loose connection etc
How much fuel is in the tank according to the fuel gauge?
It may sound strange but low fuel (below 1/4 of a tank combined with a sudden swerve and jolt like above can often cut the flow to the pump although not necessarily trip the fuel cut off switch... I have been there and got the T-shirt and it took two full 5 ltr fuel cans to get the car started again as a result. So worth a try
Has the car had a recent history of slow starting and gear selection issues or was everything fine for the past month.
when you turn the ignition on and all the dash warning lights come on are any still illuminated after 10 seconds like a little key symbol?... If so it could be the immobilizer not receiving a signal from your key via a small circular aerial that is located around the ignition barrel.
These are notorious when the plug that attaches it to the wiring loom becomes loose, often with a jolt or pot hole etc... Removal of the steering column cowling and tracing the wire from the circular ring aerial to the plug, disconnecting it and reconnecting often helps...
Try those first then let us know if it works or not... It might just be that simple