However, you are only one person. I could give a counter-example, in
that it takes my husband approximately 45-50 minutes, door-to-door,
going to work by public transport. On the rare occasions he takes the
car, it takes him at least 1 1/2 hours.

Why would he take the car?

I think I've missed something here - why would people not use public
transport most of the time, but occasionally use the car when they had a
good reason to do so, such as PT not running?

Once you own a car, the cost of a journey collapses dramatically
(insurance, tax etc doesnt increase per mile), and ends up below that
of P.T. For the majority of the country a car is always faster than
P.T. London is a special case, as it's such an overcrowded ********,
but even in London its faster offpeak to travel by car.

I agree I will subject myself to the train if I have to get into work
for some unusual time like 9AM, however those are few and far between
(and last time I drove in for arround 9AM - as there were 2 trains an
hour peak time when there's normally 6) I went to heathrow, and it
ended up faster anyway.