Hi Maggie67
I have suggested this approach in other posts recently.....
I personally have found the best way to introduce you and your company, and the Benefits of using your company over all the others, is by letter first.
Call the building company up and ask for the name of the person in-charge or organising all the subcontractors. If they wont give out names, then ask for the department name to send your info to.
Generally, they will ask why you are calling, and by briefly explaining what you are doing will trigger a response occasionally.
Work out a letter of introduction which is brief and to the point and mention in it that you will give them a personal call within a day or two of them recieving the letter
During this phone call, you caould ask such questions as when any new projects are starting etc and that you would like to be considered as a company to give them a competitive quote.
Obviously it would make quite an impression with them if you send them a letter of thanks and send another buisiness card for the phone chat.
Hope this gives you an idea.
Don't worry too much about having formal training, as you can use the buildings you have done already as a possible reference, especially as you have had no complaints from your work.
All the best in your endeavours.
Regards
Tim