Hattyhar, do you utilise the Speech therapy networks that you know of ?
I'm sure they would be able to let the Preschools know about your services during informal & formal communications.
We were always pleased to recieve contact from appropriate service providers, it greatly helps in being able to keep parents informed of current news & make organising of duties much easier !
Have you considered contacting
nahps & hpset to see if they have plans to promote your/their work more widely .. publish a poster perhaps and maybe even a database of national contacts, maybe even
PALS.nhs.uk, to see if they can register a list of internal contact points that 'frontdesk enquiries can be directed to ?