Technically, with proper oil (5wX / 0wX speced for your car), proper local winterized fuel (perhaps treated with an antigel product such as PowerService White), and a good battery, and a good set of working glowplugs - neither a battery blanket nor a frostheater should be necessary. They can't hurt, however.
After working on B4's with Frostheaters, my preference is to rim them off and throw them in the trash. They are nothing but a nuisance.Battery blanket not really necessary as the FrostHeater mounts right under the battery, warming it as well as the engine.
.