Thought I'd write up a post to help a few people out. Spent 2 hours researching this today. It is possible to fit after market seats in an MB model civic without a tailored/specially fitted subframe. So for all of those that would like a sportier seat, or some racing seats, this is how you do it and what you need
List of parts:
Seat (of your choice)
Universal side mount rails
Base mount conversion rails (you will only need these if you are buying seats with base mount/bottom fitting only)
How to install seat seat:
Remover factory seats and rails from car
Remove factory rails from factory seat
install universal side mounts to factory rails ( some bolts may need to be removed or cut off) put factory rails back into car with universal mounts attached
Install base mount conversion brackets to side mounts
install seat to base mount bracket
If you have a seat that is side mounts only you will not need the base mount conversion bracket. you can skip step 4 and install the seat directly to the universal side mounts.
The great thing about the universal side mounts is that you have a lot of choice in how you can position your seat. meaning you can have more lean in the seat. be higher up or lower down. this is all depend ending on the side mounts you buy and the amount of holes available.
List of parts and seats I used to make this possible:
Seat - Sparco R100 - https://www.demon-tweeks.com/uk/sparco-r100-seat-7000253/
Side Mounts - Sparco Steel Side Mounts - https://www.demon-tweeks.com/uk/sparco-steel-side-mounts-s-s004902/
Base mount conversion - OMP Base Mount Conversion Brackets - https://www.demon-tweeks.com/uk/omp-base-mount-conversion-brackets-omphc0-0660/
Hope this helps anyone still trying to figure out how to do this.