Hi Jo
I did Makaton training a few years ago, as we had a child who used it. The only thing I would say is it is something that you have to use or lose.
I had a conversation recently with our inclusion officer as I had seen the news saying that settings were using Makaton with all the children. A few years ago there was some discussion as to whether using Makaton delayed a child's speech. the research now seems to point the other way and we are encouraged to use Makaton with children with speech and language disorders.
check out the Makaton website
www.makaton.org they maybe able to advise you re courses
Or speak to your local EYDCP who may also be able to help
good luck
BB