I'm trying to help my husband find his father, but we only have rough details like he was around 40ish, called himself Lenny worked on the building of the Western Isles hospital on the Isle of Lewis around April - July 1990 as a bricky or a roofer. Where should we start?? What questions should we ask?? Who should we ask??

Although it has been nearly twenty years the hospital should have records pertaining to the original contractors. You could then contact the company and with any luck "Lenny" may still be employed with them or they have the means to contact him. Keep in mind he may or may not desire to have a relationship with your husband.

Does your husband have a birth certificate? So that we can get the exact spelling of his father's name.

I suggest that you hire a private investigator.