But Damian we don't get the Hallmark channel....

One way to find out, at least in the USA, is to go to Yahoo.com and click on TV. They have a feature that lets you enter your ZIP code and cable (or other TV service) info, and then you can "search listings" for the next 2 weeks -- for example, you can search throughout your own available channels for "Columbo".

TV Guide.com has a similar feature, but their site got so unreliable that I now prefer Yahoo.

If it helps at all, I have seen the older episodes aired on WGN (the superstation out of Chicago that runs on a lot of cable systems). They run a lot of McCloud, McMillan & Wife, and all those other old ones. When or how often, however, I cannot say.