TEACCH is a program most commonly found(though not always) in a school setting, as a method to teach kids with AS, and to enable them to work at their own level, encouraging independent completion of worksheets etc. In America where you more frequently find AS classrooms, all the kids benefit from the highly structured approach, visual learning etc .
ABA/Lovaas is a program looking at intervention at both a behavioural and developmental/intellecutal level. Primarily done in an at home 'therapy' session, but whose principles should apply to all aspects of the childs life (incl school). It is by nature very intensive, but I doubt there are very many families in the UK getting the recommended 40 hours a weeks of therapy... with the costs being just too prohibitive. I've seen some kids do amazingly well with ABA - practically losing their diagnosis, and at the same time, I've seen many who plateau at certain levels, through which ABA can not get through. Overall for behaviour it can be very helpful, especially to help parents with coping stratagies. I am not personally familiar with TEACCH so cant really pass comment on that.
