We live in the Ruislip and son has been offered a place in the Upton Court Grammar School. Anyone making similar journey willing for car share?

Do you have a back up plan of you don’t find someone suitable? Public transport looks unfeasible.

Metropolitan line to Uxbridge & then a bus to Slough town centre takes just over an hour at best. That's a lot of traveling for 7 years. Driving is about 25 minutes according to Google maps, but of course could take a lot longer in bad traffic.
There are good schools in Ickenham & Ruislip, I would focus on those if it's not too late. He would then have local friends as well.

We will have no other choice but to use school run transport companies. Failing that public transport is always an option:

From Ruislip Manor [nearest to my house, max 10 mins walk] Station to Uxbridge Station [15 mins] and then bus number 3 to Slough Town getting off at the School [40 mins] so just over an hour each way. For first few months I will be dropping him in the morning but he needs to come back on his own, not ideal but public transport is the fallback option.
Google maps link removed as it had your postcode in it

If there’s already school transport in place that’s probably your best choice rather than car shares, if you want to take a place at UG.

Otherwise your other choice is to look at schools closer to home that will be easier to get to. I don’t any any knowledge about your local schools, but Scary Mum seems to and thinks there are good schools available to you.

I’d also suggest you either try the public transport options yourself at the appropriate times or at least monitor them on line in real time for a few days to see how well they manage to stick to the timetable.

OP, have you considered moving somewhere closer? School transport (if there is any) is very restrictive for children and will make it very difficult for them to do after-school activities. And a journey of at least a bit over an hour - probably often quite a bit over an hour - each way is not sustainable.

Reading the advise above I feel like it was it was waste of time, money and effort to put your kid through torturous journey for elevenplus exercise if you are living in the part of Greater London where I am living currently. Couple of years ago situation was different as grammar schools use to give some places to out of catchment students but all of them closed their gates, I worry in coming years as population grows further catchment will tighten even further.

I suspect you are right. I wouldn’t be surprised if Upton Court follow Herschel and Langley and start giving more priority to local children over those who have to travel from much further afield. This of course could have an impact on any school transport (whether school organised or private) as it will get less and less feasible to run for the few remaining students who do need it.

I can understand your frustration, but travel to school is something all parents need to consider when looking at schools, what exams to prepare their DCs for, which ones to put on their CAF etc. Schools themselves are starting to look at the impact of long journeys on their students too, and most want to limit travel times. It does impact DCs and their learning, plus it also effects their ability to get more involved with other school activities. Activities that could benefit both school and student.