It is a very large school, but we haven't found it a problem in terms of individual attention - I was actually surprised at the amount the staff seemed to pick up on regarding my DD.
I had phone calls from the Languages Dept regarding the struggles DD was having and the best way to go forward in both Y7 and Y8. Calls from the Science Dept when DD was quite clearly taking the poor teacher for a complete ride - we devised a strategy together to put a stop to that. And an email from the Art Dept in Y7 offering DD a graphics scholarship and specialist classes after school (I had no idea she was any good at that!).
I do keep in touch with the form tutor, and with the Head of Learning and they have always been extremely prompt in returning emails or calls - normally within a couple of hours and always the same day.
For context, DD is in Y9, with SEN and on a music place. She is a very confident child and has no problem in going and telling Heads of Year if she's not happy about something and advocating for what she wants, which probably makes it easier than if she was very shy and kept everything to herself.
Regarding trips, we didn't have any in Y7 due to Covid, but the Y8 trip to Paris was open to everyone. The Easter Science trip to France was clearly advertised as having limited spaces and that if oversubscribed they would pick names out of a hat. Other trips that DD has done have either been subject specific where everyone in the class has attended, or have had priority for scholars. Recent ones were the Gospel Choir day where music scholars specialising in singing were expected to attend (but others who were interested could), and the trip to the Royal Opera House where priority went to music scholars and those doing GCSE music. All explained in the emails that were sent home for permission/safe guarding sign up.
With clubs, things like horse riding they do rotations - but most of the others you can just sign up. You do have to be proactive though - the clubs, competitions and extra curricular are all optional and nobody will chase if your child doesn't want to do them.
Positions of responsibility - they seem to endlessly advertise for kids to put themselves forward to be Head of Houses. Junior Prefects have been recently appointed in Y9... 50 of them I believe. DD said she had to sign up and that you needed to have a certain level of attendance and behaviour points to qualify. Not sure how it worked for Y10. For things like school tours they ask for volunteers - it's not pre-selected.
We've been very happy with the school so far - but it is probably one that will suit some children more than others. There were schools we looked at and disliked so much we ran away from the open day, but that friends liked so much they sent their children there and love it. Horses for courses...