This just-published paper provides more information on the occurrence and distribution of Thaumastocoris peregrinus in Portugal. On this occasion it also appears to have arrived together with a predator apparently picked up in South America!
Garcia A, Figueiredo E, Valente C, Monserrat VJ, Branco M (2013) First record of Thaumastocoris peregrinus in Portugal and of the neotropical predator Hemerobius bolivari in Europe. Bulletin of Insectology. 66(2):251-256