It sounds like 'Intimate Contact' with Daniel Massey and Claire Bloom though it was 1987 according to The Internet Database. I think I remember watching this. Didn't the lead actor have a habit of picking up young men on trains??
This reminds me of 'Closing Numbers' ~ a brilliant drama starring Jane Asher. I can't remember if her husband became HIV +, but jane's character became an HIV 'buddy'.