All employers need to match 3% of your salary and you pay in 5% unless you’ve opted out. Check your company handbook / policies - my company offer two scheme but you have to opt into the better one which is worth much more.
You’ll get tax relief on pension contributions but if you value the flexibility more than an ISA is a decent solution. I think you’re on the right track.
There is a great thread which is worth a read through about setting up passive investments, I found it invaluable when I brought my pension over to :freetrade: