Thermal lining for tab top/ring top curtains

BB78

Even though I've got brand new upvc double glazing my windows seem draughty & cold, I'm thinking of using thermal linings but the problem is one set of curtains are tab top and the other are ring top and all the ready made linings I've found so far are for pleat curtains!
The tab tops are 52" x 66" and the ring tops are 90" x 90", I'm not too bad with a needle and thread but don't want to ruin the curtains, does anyone sell ready made liners for anything other than pleat curtains or should I buy thermal lining material and line them myself?

froogirl

I don't know if anyone sells the ready made linings your require, but one way to do it yourself would be to hem the lining fabric on all sides and then attach it to the curtains at the top with velcro, to make them easy to wash and/or convert for summer.

BB78

Dunelm Mill have ready made linings 51" x 66" for £11.99 and 90" x 90" for £22.99, could I use these and velcro them on? or is it cheaper to buy the material?
If I buy the material can someone please help me with how much I need please?? I'm no good at converting and working out measurements!!