It's available on several abandonware sites and have been for several years. While the developer still is around, back in the days, it was common that the IP was owned by the publisher (think for example about publisher SCi which took Carmageddon away from Stainless Games and gave it to Torus for TDR2000). Virgin Interactive is not around as its assets was sold to Titus Software in 1999, which turned into Avalon Interactive in 2003. Both Titus and Avalon are defunct/bankrupt and my guess is that the rights to Screamer 2 and Rally (as well as many other games) are in limbo. On GoG.com you can only get Screamer 1, but that game was developed and published by different companies.

This working patch needs the lines Davros mentioned for the colours to show up right.