There's a rather serious problem with this ad, apart from the fact it's utterly awful.
The conceit of two women called Pam and Fern, because it supposedly sounds a bit like Planitherm, is designed to make you remember the name. Planitherm. It sounds like Pam'n'Fern. See?
Only it doesn't. Planitherm, to me, brings to mind some sort of sanitary product. Pam and Fern brings two idiotic housewives to mind. And that's it.
Perhaps if you they called Plani and Therm they would sound a bit like Planitherm. Think about it:
Plani: Hello Therm.
Therm: Hello Plani.
Plani: Have you seen them lot over there, they've got some new double glazing in.
Therm: Double glazing? Are you drunk? The economy's in ruins, we're going to war with iran and you're burbling on about double glazing?
Plani: Umm, sorry. Why do you have a pen in your hair?
Therm: Because I'm mentally unbalanced.
Plani: Uh, OK. By the way, the new double glazing - it's called Planitherm. That's a bit like us, isn't it?
Therm: What in God's name are you dribbling about, you stupid woman?
Plani: Well, it's like our names isn't it? Plani and Therm - Planitherm. See?
Therm: ...keep away from me. KEEP AWAY FROM ME!