It is as real as it gets without actually flying a plane. You are right, £320 is a fair amount of money but as noted
in the thread, this is a very good price for an hour in a full motion simulator in the UK. You won't get a full motion simulator cheaper anywhere.
You should just concentrate on the flying bit in the hour, so do a few take-offs and landings under different conditions. The time will certainly feel like it goes fast. It can be a bit overwhelming, but really you only need to concentrate on a few instruments and your pilot instructor will take a lot of the workload to make it easier for you.
I have also done the one hour trial flights in a cessna/PA28 and they aren't really comparable. If I were you I would do both. Trial flights can be as little as £120 an hour depending where you are.