They always allocate you a seat. You can change them at absolutely anytime only by paying. I'm gold and I always call them and have to pay to move to the front a few days after making the booking. Note that their check-in opens 3 days before travel. I always book as a BA codeshare through BA but still receive an email check-in reminder directly from Loganair on about the 3 day before travel mark. They have some unusual routes. My next one is Aberdeen to Norwich.