Let's try and make some sense of this
The law demands that each local council issues to its residents who have reached the required age a pass which allows them to travel on registered local bus services free of charge any where within
Britain between the hours of 930- 2300 Mon-Fri and all day Sat / Sun & Bank Holidays .
Other pass schemes work in Scotland & Wales and Northern Ireland.
Operators must accept local passes And ANY other pass issued by any council the local Council (or PTE's or county or TFL depending on area) will then reimburse the operator for the journey.
The disabled pass is available to any one who who as certain conditions or who is unable to obtain or as lost their driving licence due to a medical problem which prohibits them from having a licence - this does NOT incude certain drug or alchol related conditioins. Epilepsy is one of the conditions that allow people to get a pass unfortunatley this is not publiced very well and is not well know about.
Councils may extend the "free" travel to include earlier or latter times and may include other forms of transport : tram/ train/ ferry / cable cars etc.
The passes are not valid on national express - unless its registered as a local service - or on tourist services including those that include admission to a venue as part of the ticket. Where a council extends the service it is up to the council to decide if it allows people from outside the area to take part in the extended benifitts.
As mentioned above there is also a "disabled" pass this allows travel all day and in some areas a "helper " pass is also issued to them, however some areas do not accept the "helper " pass from other areas.
I assume that the open top service is no registered as a local service or is a tourist service.
I have looked on the IOW website which isnt very usefull
http://www.iow.gov.uk/council/departments/engineering_services/transport_fleet/Public_Transport/
Looking at the local bus operators site (southern vectis) the open top service is advertised as a tour so therefore the passes arnt valid - however , from the information above it appears that the local council allows there passes to be used.
http://www.islandbuses.info/otdowns.shtml
Details of disabled passes (taken from the site below)
Who is eligible for a disabled person's bus pass
You're eligible for a disabled person's pass if you live in England and are 'eligible disabled'. This means you:
are blind or partially sighted
are profoundly or severely deaf
are without speech
have a disability, or have suffered an injury, which has a substantial and long-term effect on your ability to walk
dont have arms or have long-term loss of the use of both arms
have a learning disability
You're also eligible disabled if your application for a driving licence would be refused under section 92 of the Road Traffic Act 1988 (physical fitness). However, you won't be eligible if you were refused because of persistent misuse of drugs or alcohol.
Full details
http://www.direct.gov.uk/en/TravelA.../DG_10036264?CID=TAT&PLA=url_mon&CRE=bus_pass
hope the above information helps
(On a lighter note before this came into place as a planning exercise I sat down and worked out you can get from where I live in sheffield to London in 13 hours using 14 trains - ironicly I dont get my pass till the year 2026)