Hi Lisa,
The optimate lead is simply a direct connection to the battery and depending on which lead they fitted may already be fused. Providing it's a genuine Optimate lead it will handle the 1.2 Amps without issue. You can plug directly into it, but as Graham said, better be safe than sorry and make sure either the Optimate lead already has an in line fuse or fit one in the lead to the gloves.
However... I personally think heated grips are a much better option. Then you have the flexibility to switch gloves should a pair get wet or something.
Regards,
