Hi atlash, why dont you just go and see them face to face , there is no comparison i think a quick call to ask if it is possible to call in and have a quick friendly chat regarding what your company has to offer and the possibility of tendering for any future works . im a big believer in face to face when it comes to first introductions there is a kinda honesty about it and its gives both parties an excellent opportunity to get to know a little bit about who they are dealing with and helps with future contact aswell by means of for example the person might be the type that likes a good joke by email, he might be the old fashion type person who prefers faxes, letters or phone calls because technology passed him by. you may also get to know things more personal like he has an 8 yr old daughter who loves horses and goes to lots of competitions, so the nxt time you speak to him/her you ask how many rossettes the little girl has been winning lately.
we do use basic intro letters generally as a mass mail out of flyers to small building , roofing firms etc which we say , we are writing to introduce our company, so they may consider us for any future projects , tell them what services we offer blah blah blah
but if it is a company that we think is a company we would like to work for we pick up the fone and arrange a quick meeting take some cards, pens or summit useful with our name on it, and discuss what they look for in a company , how they do business etc etc just general work chit chat but also very important you also find out if they are the type of company you want to work for, when they pay, are they approachable if you have problems, what is their view on health an safety, how is their operational procedures etc you can find all this out by discussing what they look for in a company how they would expect things to happen from tender to final account.
A god honest friendly face to face introduction in my book beats everything else if its too far to travel try asking bout video conference. you can then put an introduction pack together based on your conversation covering the main topics discussed