Conversational Software Limited (AI, Pop2 compiler)
3L (Imp, C, Pascal, Occam compilers for many architectures; Shapesmith)
Edinburgh Portable Compilers Ltd (Imp, Fortran compilers)
An Teallach Ltd
Rhetorical Systems - PeterDenyer
Algotronix founded in 1989 by Irene Buchanan, John Gray and Tom Kean.