It's a 98dB day and you should be OK on a stock M3W exhaust - mine was about 95dB.
After upgrading to MMC Stage 1 it just scraped in (it was over but the noise marshal wouldn't tell me by how much!). It took a couple of goes and required raising the revs very, very slowly.
If you're near enough you can always ring them up and go for a noise test at another trackday beforehand.
