If you bought the recaro cs vinyl seats you could have them retrimmed like the nismo ones for less than the cost of upgrading to leather.
There was a German eBay seller a few years back selling recaro cs seats for a lot cheaper than they are over here. They are similar to the BMW motorsport seats for the e92 m3, so a lot of people on the m3 forum bought them as a alternative. Might be worth having a look.
Having said that, it was pre brexit referendum. So any saving has probably disappeared.
These are are in the classifieds currently.
They would look great retrimmed like the nismo ones.