I live North West of LHR in the area called 'The Chilterns' which is itself north of the Thames Valley.
I have been using LHR from this neck of the woods (West Hertfordshire) for nigh on 18 years and will not bore you with the details.
Suffice to say, I have tried public transport but, living in a village means that I start at a disadvantage. Taxi and coach get me to LHR in about 1.5 hours. A car takes me between 35 and 55 minutes depending on time of day. A taxi ride is about GBP50, depending on company. If I pick up a black cab from LHR to home - it is GBP65.
After all these years, I know every possible alternative route when one of them clogs up, whereas the coach driver has to stick to his route and sits in the jam.
When I meet someone off an 11 hour flight at 07:00, am I really going to inflict British/London Transport on them?
Congestion charging at LHR is a good idea in principal BUT the practicalities mean that business will be hit with higher charges. Regular folk that use it once a year will mind - but will pay.
Which leaves those free-lance and small biz people (like myself) who then have to pay everything out of their own pocket. Sometimes I use/visit LHR only six times in a year but 10 or 12 is the more common figure.
Congestion charging for London itself is reasonable because all roads and railroads lead to London. They do not all lead to LHR.